Five Questions on Polarization and International Politics

You frame your book in terms of advantages democracies have in the conduct of foreign policy. What are these advantages and how did you come to this framing?

The idea of a “democratic advantage” comes from a long tradition of scholarship in international relations arguing that relative to non-democracies, democracies tend to have better outcomes in foreign affairs. This book focuses on three democratic advantages. The first is stability: the fact that democracies maintain pretty stable foreign policies over time, despite regular elections and leader turnover. The second is credibility, the idea that democracies can more credibly signal information to their adversaries abroad. The third is reliability—democracies can reliably maintain commitments to their allies.

These advantages stem from the fact that leaders in democracies are accountable, both to the public through regular elections and to other actors within government, like opposition parties, a legislature, or a judiciary. Democracies leverage these constraints to secure better outcomes in international politics.

The democratic advantage is one of the most powerful, pervasive ideas in international relations theory. It is foundational to a lot of scholarship on the domestic politics of international relations. And I became interested in understanding how rising polarization within many democracies might undermine these advantages.

As you say, the model undergirding your book points to how polarization erodes these advantages. But you first have to navigate the problem of who is polarized. Do you see this mostly as an elite or mass public story? And how does polarization erode democratic advantages?

Political scientists typically distinguish between two types of polarization. Ideological polarization is increasing policy distance between parties, often on a left-right or liberal-conservative spectrum. Affective polarization is increasing social distance between parties, conceptualized as a tendency to like your own party—and members of it—but dislike the opposing party and its constituency. In the United States, we have clear evidence over the last three decades that both ideological polarization among elites (specifically, Congressional polarization) and affective polarization among the public have substantially increased.

But what we’re seeing across many democracies today is that ideological and affective polarization may be reinforcing one another, fueling a sort of extreme polarization. Consider how polarization could undermine the ability of the United States to be a reliable ally. As the public grows more polarized, they are less likely to abide by democratic norms and procedures around entering into and exiting from international agreements. Instead, citizens care more about seeing their preferred policy. As politicians grow more polarized, Congress is also less able to effectively check presidential power. As a result, presidents are more likely to act unilaterally in foreign affairs, making and breaking international commitments when doing so benefits their short-term political interests.

In the United States, one way this has played out is that presidents increasingly enter into executive agreements or non-binding political commitments rather than going through treaty processes that require supermajority support in the Senate. These agreements do not require such bipartisan support, and it is easier to withdraw from them. In the long run, such agreements make the United States appear less reliable.

One interesting aspect of the book is your use of both surveys and experiments. It seems hard to compare whole countries around the theme of polarization because of data constraints. But you get at it through evidence drawn from the United States and individual voters. How did you approach the evidence?

This book was never going to have one smoking-gun piece of evidence. Rather, it uses many empirical approaches to illustrate different parts of the argument. One approach was a descriptive, cross-national analysis of trends in polarization and foreign policy outcomes across countries and over time. This involved a large data collection effort to measure different forms of polarization at the country-level, including new measures of polarization in foreign policy.

But what most interested me were the particular pathways through which polarization undermines democratic advantages and that necessarily had to be grounded in a particular institutional context. The second empirical approach was to do a deeper dive on the United States using a combination of public opinion surveys and survey experiments, descriptive data about the behavior of politicians, and qualitative evidence from cases.

Public opinion surveys can illustrate how heightened partisanship might erode constraints on democratic leaders. For example, in one survey experiment conducted before the 2024 U.S. presidential election, I asked 4,000 Americans to read and react to hypothetical crisis scenarios. Half of the survey respondents were told to imagine a scenario in which Democratic candidate Kamala Harris was elected, and the other half imagined the same scenario in which the president was Republican candidate Donald Trump. Survey respondents were told how that president responded to a given crisis with an adversary of the United States. The survey found that respondents tend to approve of the response of their co-partisan president but disapprove of the exact same policy when it is enacted by a president from the opposite party. These effects are even stronger among strong partisans. Overall, these findings suggests that as polarization increases and Americans adopt stronger partisan identities, electoral accountability over foreign policy is undermined.

You chose the negotiation of President Obama’s Iran deal—the Joint Comprehensive Plan of Action or JCPOA—as a case study of the consequences of polarization for foreign policy. I was struck by your observation that polarization on Iran preceded the first Trump administration. What did you see in this case with respect to your core claims? Does the current war shed any more light on the effects of polarization given that some portions of Trump’s base seem opposed to it?

One reason the JCPOA case is interesting is because, in theory, partisan disagreement should be a good thing when negotiating with an adversary. Democratic leaders can leverage disagreement between domestic actors to extract concessions during international negotiations. For example, democratic leaders can go to their foreign counterparts and credibly say things like, “There is no way that Congress will ratify this agreement as it currently stands, so we need to make a better deal.”

The JCPOA negotiation, however, illustrates how more extreme forms of polarization upend this advantage. During the negotiation, the U.S.-Iran relationship became increasingly politicized in the lead-up to the 2016 Republican presidential primary. Congressional Republicans had incentives to flagrantly contradict what the White House was doing and perhaps even attempt to derail negotiations. One well-known example of this is the open letter that Senator Tom Cotton wrote to Iranian leaders saying that any nuclear deal Iran reached with the Obama White House could easily be reversed by a subsequent Republican president.

In the very early days of the nuclear deal, many people in the White House thought that more moderate Republican legislators would support a nuclear agreement with Iran. The deal ultimately became heavily politicized, however, and was concluded without bipartisan support. As a result, the JCPOA was a much less durable agreement, and the Trump administration subsequently withdrew.

I hesitate to draw direct connections to what happened with the JCPOA and the war with Iran, simply because it’s hard to speculate about what might have happened if the United States had stayed in the agreement. But there are some interesting thought experiments. If Congress was less polarized during the Obama administration, would there have been some version of nuclear agreement with Iran that would have been supported by both parties? Would that agreement have been more durable than the JCPOA was? Could such an agreement have prevented the conflict we are currently in?

With respect to what the current war in Iran tells us, one of the main takeaways from these early days is that partisanship trumps ideology in public opinion about foreign policy. Foreign military intervention in the Middle East is pretty inconsistent with the American First foreign policy agenda that President Trump campaigned on. Nevertheless, a large majority of Republicans support Trump’s actions in Iran, while a large majority of Democrats oppose them. This fact underlines how hard it is for a highly partisan public to hold its elected leaders accountable for foreign policy decisionmaking. President Trump has been able to unilaterally enter into a conflict with Iran without facing any real constraints from Congress or the public, at least so far. Those constraints might ultimately affect the ability of the president to reach an agreement. But it’s hard to argue that polarization hasn’t eroded constraints on presidential power.

Where might polarized parties find common foreign policy interests or are we doomed to ongoing polarization on foreign policy? Could membership in NATO become another point of division or do you believe that bipartisan consensus will allow our commitments to Europe to hold?

Funnily enough, I didn’t set out to write a depressing book! In fact, one of the things the book emphasizes is that in comparative perspective, the United States tends to have much lower polarization in foreign policy relative to its peers. There are many other democracies where foreign policy and security policy are more central to party politics—South Korea, Taiwan, and Israel all come to mind. However, we are starting to see the gradual extension of partisan conflict to a wide range areas of foreign policy in the United States, including immigration and refugee policy, climate security, tariffs, and the Gaza war.

However, I can think of broad issue areas in foreign affairs that are not so hopelessly politicized. Historically and presently, there has been a lot of Congressional interest in sanctioning adversarial regimes and, although there is a much larger debate about the efficacy of economic sanctions and similar tools, they tend to receive substantial bipartisan support.

A second area where we see a lot of bipartisanship in Congress is around investment in economic and technological competitiveness in a renewed era of great power competition. Both the Trump and Biden administrations have prioritized this, although debates persist about exactly how and where to make those investments.

A third area that remains bipartisan is investment in national defense. Relative to comparable processes, the National Defense Authorization Act process that underpins the annual defense policy bill tends to be less politically charged. In general, there are few electoral incentives for legislators to strongly advocate for reductions in defense spending.

Finally, we see substantial bipartisan support in Congress for legislation that aims to protect civil liberties abroad. This is a common way that legislators use their public platform in foreign affairs. Bipartisan coalitions of legislators engage in human rights advocacy, for example, to free political prisoners or condemn repressive regimes.

To be clear, there are aspects of each of the issue areas that I mentioned that are politicized, but they have still not been fully absorbed into the partisan divide. While we are observing an uneven process of increasing polarization in U.S. foreign policy, there are many areas where bipartisan cooperation remains possible.

Rachel Myrick is the Douglas & Ellen Lowey Associate Professor of Political Science at Duke University. Her research explores how partisan polarization affects foreign policymaking in democracies, with an emphasis on US national security policy. 

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