🔎 The Puzzle and Two Possible Paths

A common explanation for growing polarization in American foreign policy points to an absence of external threat. Two mechanisms could reverse that trend: an information mechanism, where clear evidence about an adversary prompts bipartisan agreement among policymakers; and an identity mechanism, where an external danger raises national identity above partisan identity and reduces affective polarization among the public.

📜 How Congressional Speeches Were Used to Track Partisan Shifts

Study 1 applies computational text analysis to congressional speeches to see whether security threats reduce partisan differences in attitudes toward foreign adversaries. The analysis tests whether language and framing about adversaries converge across parties during security crises.

📊 What Public Opinion Polls Reveal About Affective Polarization

Study 2 draws on public opinion polls to assess whether external threats lower affective polarization—that is, negative feelings toward political outgroups—among the American public when threats become salient.

🧪 Testing Threat Effects Directly With a China Experiment

Study 3 uses a survey experiment that heightens a security threat from China to evaluate both the information and identity mechanisms in a controlled setting and to observe how threat messaging interacts with the domestic political environment.

💡 Key Findings

• Evidence is limited that external threats produce broad bipartisan convergence in congressional rhetoric or policy preferences.
• Public opinion data show little consistent reduction in affective polarization when threats are made salient.
• The survey experiment elevating a China threat does not provide strong support for either mechanism on its own; reactions depend heavily on the domestic political context in which the threat is presented.
• Overall, the external threat hypothesis has limited power to explain polarization in U.S. foreign policy or affective polarization among citizens.

🔍 Why It Matters

These results challenge expectations that new foreign threats will automatically generate cross-party unity. Instead, responses to external dangers appear shaped by the domestic political environment and cues present when threats are introduced, with important implications for scholars anticipating bipartisan consensus and for policymakers seeking to build unified responses to international crises.