By virtually any measure, American domestic politics are at their most polarized point in decades. Members of Congress are increasingly unwilling to compromise, the national media landscape is fractured, and public opinion is fragmented. Recent scholarship suggests that foreign policy issues have taken on a similar polarized character. However, a select few issues, such as infrastructure reform, have managed to remain somewhat outside the bounds of extreme partisan disagreement. In the realm of foreign policy, one might think that nuclear weapons debates — given nuclear weapons’ taboos, their immense implications for national security, and the (fortunate) lack of empirical data about their use in combat — would be one possible candidate for avoiding immense partisan strife.
In this essay, I examine the political polarization of nuclear weapons issues in the United States, a topic that (to my knowledge) has never been studied before. To approach this topic, I reviewed all mentions of nuclear weapons in every Democratic and Republican national party convention platform since 1948, the first Presidential election year after the first (and only) use of nuclear weapons in combat in the 1945 bombings of Hiroshima and Nagasaki.
I find that the partisan history of American nuclear weapons issues is best separated into five distinct periods, listed in Figure 1 below. Curiously, while points of agreement have come and gone throughout the periods, all major points of disagreement have stuck around indefinitely after entering the national debate. Most interestingly, virtually all disputes between the parties neatly sort themselves into five divergent issues: issues where one party’s position, from the time it was adopted, has (1) been the constant policy of that party and (2) never been adopted by the opposition. The accumulation of these five permanent areas of disagreement — International Negotiation, Missile Defense, Test Ban, Spending, and End Goal — along with their increasing severity in more recent decades, has led to increased polarization over time.
Below, I first offer an explanation for this phenomenon, and then outline each of the periods in turn.
What caused the development of these disagreements? Drawing on Jeong and Quirk, I argue that they were a result of crisis-based party competition. This theory holds that when crises demonstrate the military weakness of the United States, they fundamentally alter the political landscape of nuclear issues, with two main effects. First, crises reorder priorities: in the aftermath of a crisis, Americans become concerned about preventing a similar crisis in the future, leading to new policy goals. Second, although the current administration gets a short boost in approval during a crisis (the so-called “Rally ‘Round the Flag” effect), crises create polarization in the long term; by bringing nuclear superiority issues to the forefront of the national conversation, crises encourage parties to try to win votes with differentiated visions for the future of nuclear policy. In other words, the parties often draw different lessons from the same crisis — stoking existing areas of disagreement and leading to new, fundamental disagreements that are seemingly permanent., 
Indeed, the emergence of the disagreements above very neatly lines up with three points of crisis that demonstrated American military weakness: the 1962 Cuban Missile Crisis, the 1973 end of American involvement in the Vietnam War, and the September 11, 2001 terrorist attacks. Thus, I have I’ve used these events, and the 1991 fall of the USSR, to bookend my periodization.
In the coming sections, I sketch out the five periods of American nuclear politics that I have I’ve defined above:
I. NOVEL NUCLEAR CONSENSUS (1945—1962)
At the start of the Atomic Age in the United States, the two parties held broad agreement on nearly all nuclear issues. Within this Novel Nuclear Consensus, three major points of agreement emerged. First, deterrence became the principal nuclear priority for both parties. For example, in 1952, the Democrats stressed the need “to build all the atomic and hydrogen firepower needed to defend our country,” while the Republicans supported building “atomic energy weapons in abundance” to prevent a “sudden [USSR] attack.” Second, both parties agreed that the US should create arms control agreements with other nations. Finally, both parties mentioned the need for strong civil defense — that is, creating plans to defend the civilian population against the novel threats of the nuclear era — in 1956 and 1960.
Given the novelty of nuclear weapons at this time, no substantive policy differences emerged during this era; virtually all disagreements were attacks on the party in power for not doing enough on nuclear issues. For example, in 1952, the Republicans blamed the Truman Administration for allowing the Soviets to gain possession of the atomic bomb. The Democrats responded in 1956 by attacking President Eisenhower for prioritizing balanced budgets and tax reduction over strengthening the military.
II. MID-COLD WAR: WEAKENED CONSENSUS (1962—1973)
In the middle of the Cold War, the parties added two new points of nuclear consensus to the three above, but also saw their first fundamental disagreement emerge. The first of the five points of agreement was, as before, deterrence. Second, both parties modified their positions on arms negotiations to stress the need for enforceable arms control agreements. Most notably, both parties supported the first Strategic Arms Limitation Talks (SALT I) between the (Republican) Nixon Administration and the Soviets — the talks were hailed by the 1972 Democrats as an “important and useful first step.” The resulting Anti-Ballistic Missile (ABM) Treaty was ratified by the Senate in 1972 with massive bipartisan support: an 88-2 vote. Third, civil defense was again promoted by both parties in the 1964 election, but was not mentioned again, likely because national defense priorities in 1968 and 1972 were more focused on the Vietnam War.
Fourth, likely inspired by President Eisenhower, both parties stressed the need for efficient spending in the nuclear domain. In 1968, Republicans railed against “the cumbersome, overcentralized administration of the Defense Department,” while the Democrats promised to eliminate “waste and duplication.” Finally, as other nations experimented with new nuclear technologies during this period (especially the USSR), both parties called for massive increases in nuclear R&D to maintain an American technological edge.
However, in the aftermath of the Cuban Missile Crisis, this period also saw the emergence of the first divergent issue: the Republicans advocated for spending more on nuclear defense than the Democrats. For example, in 1964, Republicans accused Democrats of allowing “non-military considerations… to reverse professional judgment” on military spending.
III. LATE COLD WAR: STRONG POLARIZATION EMERGES (1973—1991)
The Late Cold War marked the first period in American nuclear weapons history where there were more points of substantive disagreement on policy than points of agreement. Three points of agreement remained from the prior period. First, while the parties disagreed over how many weapons to build (see below), there was still a clear consensus for maintaining a deterrent to Soviet aggression. Second, both parties supported well-enforced arms control measures. The Intermediate-Range Nuclear Forces (INF) Treaty, negotiated by (Republican) President Reagan, was widely supported by both parties — in 1988, the Democrats called it a “commendable first step.” The Treaty was ratified by the Senate in 1988 with a 93-5 vote. Finally, both parties called for increased efficiency in defense spending in nearly every election in this period.
However, the late Cold War saw four points of contention between the parties, likely stoked by the American retreat from Vietnam. First, the parties split on their philosophies for conducting international nuclear negotiations. Republicans, who called for “peace through strength,” hoped that a strong military would grant immense negotiation leverage and prevent future Vietnam-like snafus. In contrast, Democrats hoped to conduct more international deals and spend less on defense. For example, in 1984, while Democrats proposed the “vigorous pursuit of nuclear arms control” and the resubmission of multiple nuclear arms treaties to the Senate, Republicans asserted that arms control was “not an end in itself,” but rather a tool that was “a major component of a foreign and defense policy.”
Second, in what may be the most hotly-contested nuclear weapons issue in American history, President Reagan’s 1983 Strategic Defense Initiative (SDI) plan called for the establishment of a space-based missile defense system — a position so staunchly opposed by the Democrats that they called for an outright satellite weapons ban in their 1984 platform. Even though the 1984 Democrats made it clear that they did not take kindly to Reagan’s “futile Star Wars schemes,” Republicans dug in their heels: in their 1988 platform, they made clear that President Bush would not negotiate on SDI.
Third, Democrats in 1976, 1980, 1984, and 1988 called for a comprehensive ban on nuclear testing through the Comprehensive Nuclear Test Ban Treaty; Republicans never adopted this position.
Finally, the parties maintained their earlier split on spending: the 1976 Democrats quipped that “the [Republican] Administration has forgotten that we are seeking not to outspend, but to be able to deter and, if necessary, outright, our potential adversaries.”
IV. UNIPOLAR HEGEMONY: POLARIZATION REMAINS (1991—2001)
In the aftermath of the Cold War, nuclear priorities shifted to adjust to the end of the Soviet threat — creating new points of consensus among policymakers. First, both parties maintained their agreement on the need for deterrence, albeit using a smaller force. Second, both parties advocated for a decrease in the size of the nuclear arsenal in the early ‘90s, and for an increase in defense spending in the mid ‘90s. Third, both parties shifted their focus toward preventing the proliferation of nuclear weapons, especially to rogue states like North Korea and Iran. For example, in 1992, the Republicans pledged to prevent “outlaw nations” like North Korea, Iran, Iraq, Libya, and others from acquiring WMDs, while Democrats pledged to “get tough” on those that peddle nuclear technologies. Furthermore, both parties also focused on reducing Russia’s arsenal and ensuring that Soviet weapons did not fall into terrorists’ hands.
However, the four fundamental disagreements from the Late Cold War period remained. First, disagreements over international negotiation persisted: in 1996, Democrats praised President Clinton’s negotiations with North Korea, while Republicans promised to end President Clinton’s “efforts to appease North Korea by rewarding treaty-breaking with American taxpayer-financed oil and nuclear reactors.”
Second, President Reagan’s SDI missile defense program still loomed large. Republicans believed that SDI would enable a dramatic reduction in offensive nuclear weapons spending, while Democrats thought it best to spend slightly more on offensive weapons and avoid the “unproven, expensive, and ill-conceived” SDI plan (as described in their 2000 platform). Moreover, in 2000, Democrats attacked the Republican missile defense plan for violating the 1972 Anti-Ballistic Missile (ABM) treaty. In response, Republicans advocated for a renegotiation of the treaty.
Third, the tension over a comprehensive nuclear test ban came to a head. In the 1999 vote on the Comprehensive Nuclear Test Ban Treaty, every Democratic Senator voted for the treaty (44-0), while nearly all Senate Republicans voted against it (4-51). In 2000, Democrats called this move by Senate Republicans a threat to “both our security and our global leadership.”
Finally, even as the parties agreed on the directions that military spending should move during this period (down at the end of the Cold War, up in the mid-1990s), Republicans always wanted to spend more than Democrats.
V. WAR ON TERROR AND ROGUE STATES: HYPERPOLARIZATION (2001—2020)
During the War on Terror and beyond, Democrats and Republicans were driven even farther apart on nuclear issues, though both parties increased their emphasis on stopping nuclear terrorism. There were four major points of agreement in this period. First, both parties maintained their emphasis on maintaining a nuclear deterrent. Second, in the aftermath of the September 11, 2001 terror attacks, both parties shifted their nuclear weapons policies towards stopping terrorism, often using nearly identical rhetoric.
Third, both parties also agreed on the need to work with the international community to prevent nuclear proliferation. For example, in 2004, both parties agreed that the Six-Party Talks to denuclearize North Korea should be maintained, and also supported a broad international coalition to stop proliferation. Finally, a key point of this anti-proliferation strategy was the end of global production of weapons-grade material, which both parties supported.
However, with the parties eager to differentiate themselves after 9/11, the four previous points of disagreement saw amplified levels of partisan conflict in this period, and a new fundamental disagreement emerged. First, this period saw unprecedented division between the two parties’ international negotiation strategies. In December 2001, President Bush withdrew from the 1972 Anti-Ballistic Missile (ABM) Treaty to increase American missile defense capabilities, a move that Democrats staunchly opposed. Further, in 2012, Democrats praised President Obama’s New START treaty with Russia, and attacked Republican nominee Mitt Romney for objecting to the treaty. Most recently, in what may be the most polarized nuclear issue of the last decade, President Trump decided to withdraw from President Obama’s Joint Comprehensive Plan of Action (JCPOA) Deal with Iran, angering Democrats.
Second, while explicit calls for space-based missile defenses stopped appearing in the Republican platform, Republicans still consistently called for missile defense systems in this period, while Democrats did not.
Third, in every platform year in this period except for 2004, Democrats called for the ratification of the Comprehensive Nuclear Test Ban Treaty — a position that the Republicans never adopted.
Fourth, as before, Republicans wanted to spend more on nuclear weapons than Democrats in this period. In fact, the most polarized nuclear spending disagreement since the Reagan years emerged in 2016, as Democrats opposed what they viewed as “excessive” Republican spending to modernize the nuclear arsenal.
Finally, in 2008, 2012, and 2016, Democrats listed “a world with no nuclear weapons” as a long-term goal of their foreign policy program, a position that Republicans did not adopt.
Overall, my analysis suggests that Americans can expect that partisan rhetoric and political considerations will continue to impact substantive nuclear weapons policy for years to come. Americans can also expect that a hypothetical future crisis which demonstrates American military weakness will reorder nuclear priorities and draw the parties farther apart. I am hopeful that these results will serve as a cautionary tale for upcoming nuclear policy debates, as the United States has an interest in keeping our nuclear weapons policies as bipartisan as possible.
Thank you to Professor Stephen Rosen, Dr. Sergio Imparato, and Sam Meyerson for their immense help in assembling this essay.
 James M. McCormick and Eugene R. Wittkopf, “Bipartisanship, Partisanship, and Ideology in Congressional-Executive Foreign Policy Relations, 1947-1988,” The Journal of Politics 52, no. 4 (1990).
 To improve the ease of reading this paper, party platforms will not be individually cited in footnotes. Rather, the year and political party of the referenced platform will be clearly indicated in the text. All platforms were retrieved from, and are accessible at, the University of California, Santa Barbara’s American Presidency Project website: https://www.presidency.ucsb.edu/documents/presidential-documents-archive-guidebook/national-political-party-platforms. A full website citation is available in the Bibliography at the end of this paper.
 Gyung-Ho Jeong and Paul J Quirk. “Division at the Water’s Edge: The Polarization of Foreign Policy.” American Politics Research 47, no. 1 (2019): 61.l
 For example, During the October 1962 Cuban Missile Crisis, President Kennedy possessed broad support; Republican Senator Kenneth Keating said that Kennedy had “the 100 percent backing of every American regardless of party.” However, by the November 1962 midterms, Cuba became “Kennedy’s most vulnerable point on foreign policy.” (David G. Coleman, “The Missiles of November, December, January, February……: The Problem of Acceptable Risk in the Cuban Missile Crisis Settlement,” Journal of Cold War Studies 9, no. 3 (2007): 33.)
 Other possible explanations for my findings above largely lack explanatory power. The “Polestar” unification theory (having a common enemy makes the country more unified) does not explain why Democrats and Republicans grew further apart after the Cuban Missile Crisis, and also does not explain why the fall of the USSR did not see immediate fracturing of American nuclear politics. Another idea adapted from foreign policy literature — that nuclear politics track with standard American political polarization — holds some weight over the last few decades, but fails to explain why nuclear politics diverged in earlier periods.
 For an example of the second theory in footnote 5, see James M. McCormick and Eugene R. Wittkopf, “Bipartisanship, Partisanship, and Ideology in Congressional-Executive Foreign Policy Relations, 1947-1988,” The Journal of Politics 52, no. 4 (1990).
 The 1991 fall of the USSR did not demonstrate American military weakness, and thus saw no new divergent nuclear issues emerge, but created a large enough shift in national priorities to merit delineating a new era.
 Matthew Nussbaum and Elana Schor, “Senate Ratifies ABM Treaty, Aug. 3, 1972,” POLITICO, August 3, 2017. https://www.politico.com/story/2017/08/03/senate-ratifies-abm-treaty-aug-3-1972-241170.
 Curiously, this conviction was repeated not just across the aisle in 1968: it was also echoed by George Wallace’s American Independent Party.
 I argue that this development occurred because the two parties, capitalizing on the salience of nuclear issues at the time, developed competing nuclear visions for the Mid-Cold War period to compete for votes. By the middle of the 1960s, Democrats, perhaps seeing President Kennedy’s victory in the Cuban Missile Crisis as a vindication of current policies, began advocating for smaller increases in spending than Republicans. In contrast, Republicans felt more threatened by the USSR’s advances in Cuba, and consistently proposed additional nuclear spending and the development of new weapons with nuclear capabilities, like the Trident submarine and the B-1 bomber.
 In party platforms, at least.
 “Treaty Document 100-11 – TREATY BETWEEN THE UNITED STATES OF AMERICA AND THE UNION OF SOVIET SOCIALIST REPUBLICS ON THE ELIMINATION OF THEIR INTERMEDIATE-RANGE AND SHORTER-RANGE MISSILES,” Congress.gov, Accessed May 4, 2020. https://www.congress.gov/treaty-document/100th-congress/11.
 The Vietnam War dramatically increased Americans’ perceptions of the Soviet threat in the mid-1970s; in 1969, 62% of Americans thought that American power would increase around the world — by 1974, that number was 29%. (See Tom W. Smith, “The Polls: American Attitudes Toward the Soviet Union and Communism,” The Public Opinion Quarterly 47, no. 2 (1983): 282.)
 Notably, no new disagreements emerged — likely because the fall of the USSR did not demonstrate American military weakness.
 “Roll Call Vote On the Resolution of Ratification (Resolution of Ratification to Treaty Document No. 105-28 CTBT ), 106th Congress – 1st Session,” U.S. Senate, October 13, 1999. https://www.senate.gov/legislative/LIS/roll_call_lists/roll_call_vote_cfm.cfm?congress=106&session=1&vote=00325.
 In 2004, Republicans and Democrats sounded especially similar: Republicans held that “there is no greater danger to our people than the nexus of terrorists and weapons of mass destruction,” while Democrats exclaimed that “there is no greater threat to American security than the possibility of terrorists armed with weapons of mass destruction.”
 The lapse in this policy in 2004 can best be interpreted as a desire to not be perceived as weak in the aftermath of the 9/11 terrorist attacks.
 Note that this goal was not to immediately remove all American nuclear weapons, only to take steps to eventually move in that direction.
Image: “W48 nuclear artillery shell” by United States Army , retrieved from https://commons.wikimedia.org/wiki/ File:W48_nuclear_artillery_shell.jpg, image is in the public domain.