What would have happened if Donald Trump was President of the United States, instead of Joe Biden, when Russia prepared for and then invaded Ukraine in February 2022? Would the West have shared intelligence, remained united and forcefully condemned the invasion, and supported Ukraine, as it actually did in the early months of the war? In our article in International Affairs, we answer these questions using counterfactual analysis – a rigorous thought experiment. Our broader argument is that counterfactuals, while seldom used, are a promising method to demonstrate the impact of leader personalities on foreign policy and international relations.

Our counterfactual is this: Trump won the 2020 election (which, it bears worth repeating, he factually did not). This scenario is plausible — the election was close in key battleground states. It is also a ‘minimal rewrite of history’, changing only one significant factor: the predominant U.S. foreign policy decision maker. Trump had a strong personal interest in Ukraine and Russia and he would have been central to the U.S. response to such a high security issue, as was his factual counterpart President Biden. Even if Congress or his advisors or party would have challenged Trump’s read on the situation, countering Trump’s rhetoric and forcing him to adopt pro-Ukrainian policies would have proven difficult, especially in the critical initial stages.

If counterfactual Trump were in charge, in the 2021 lead up to and the 2022 point of Russia’s invasion of Ukraine, he would not have reacted the same way that Biden did, which was key to building the quick and determined Western response. Biden himself shaped this response, including a strong verbal condemnation of Russia, political and military support for Ukraine, and coordinating sanctions. Drawing on extensive research on political leaders in foreign policy, we argue that Biden’s personality can account for these responses and that Trump’s very different persona would likely have led to very different actions, changing the outcome. 

Biden’s vs. Trump’s Personalities 

Biden is extremely experienced in foreign policy, and his style and worldviews were shaped by his time chairing the Senate Foreign Relations Committee and as an active VP in the Obama administration. He strongly believes in multilateralism, internationalism, and Atlanticism. He listens to his advisors, seeks out information, and is personally involved in policymaking. He leans toward cooperation but is sceptical of non-democratic regimes. Biden’s specific views on Ukraine are positive — as VP he worked closely with Ukraine. All of these personality features were evident in Biden’s response to Russia’s invasion of Ukraine. He was actively involved, prioritised cooperating with allies, sought out and trusted his intelligence sources, and came down firmly on the side of Ukraine and against Russia.

Trump is a different story. His lack of foreign policy experience, coupled with his business background, shaped his views of international relations, which are ahistorical, transactional, and zero-sum and include an admiration of authoritarian strongmen. Trump’s opinions of Ukraine are very negative. He sees Ukraine as corrupt and a political enemy, and as president he viewed Ukraine through the lens of his re-election bid. Trump’s so-called ‘perfect phone call’ pressuring Zelensky to investigate Biden prompted Trump’s impeachment charges. Trump’s views of Ukraine contrast starkly with his affinity for Putin. While president, Trump publicly supported Russia’s annexation of Crimea and doubted Russian interference in his 2016 election. Layered on to these beliefs, Trump’s personality traits — thin-skinned, moody, and distrustful — created a leadership style that demanded loyalty and filtered out information challenging his own views. 

Had Trump been president in 2021-22, these personality characteristics would have put U.S. foreign policy on a very different path. He would not have brought together European and other allies in a multilateral front against Russia, due to mutual animosity and suspicion. His high self-confidence and business background may have led him to believe he could personally persuade Putin or strike some sort of deal, rather than swiftly condemning Russia. Trump’s sky-high distrust would have prevented him from both heeding intelligence warnings of an imminent invasion and sharing that intelligence with allies, both key to Biden’s approach. 

Would counterfactual Trump have changed in a second term, leading to a more Biden-like response? Probably not, as his policies were rooted in his personality and personalities are slow to change. Trump may have eventually yielded to pressure from his advisors or Congress to support Ukraine, but the delay might have critically diminished Ukraine’s ability to resist Russia’s quick advance into Ukrainian territory. Would Russia have invaded Ukraine if Trump were president? We believe so. There are indications that Putin believed Trump’s foreign policy to be too chaotic to mount a unified response. Putin might have also reasoned, based on past policies, that Trump would support him over Zelensky.

Leaders in the Multiverse

Our Trump versus Biden analysis showcases the strengths of counterfactual methods, especially for isolating the significant effects that leaders can have in international relations. The differences in these leaders’ experiences, their general and specific beliefs, and their personality traits stand out as important causal mechanisms that influence foreign policy outcomes – both counterfactually and factually.

Counterfactuals highlight the contingency of international outcomes and guard against the ‘certainty of hindsight bias’ — a misplaced belief that past events were easily predictable. The method holds particular promise for scholarship on the role of leader personality in international affairs, because counterfactually replacing individual leaders closely approximates controlled experiments, with fewer ripple effects than more far-reaching manipulations of domestic or international conditions. This gives a clear view of a single explanatory factor — leader personality – and can also build on a rich array of well-established and theoretically grounded studies showing the impact of leader personalities in international affairs. This boosts the credibility of arguments about how a different leader would have influenced international outcomes in the counterfactual scenario. 

Counterfactual methods, with careful attention to both minimal manipulations and to theories linking personality characteristics to foreign policy behaviours, could plausibly be extended to other leaders’ responses to the Russian invasion. Would Merkel have changed German foreign policy as quickly as did inexperienced Scholz? Would another Italian Prime Minister, without the banking background of Draghi, have played the role of ‘sanction architect’? If the French election had happened earlier and Le Pen would have replaced Macron, where would France have stood? And then there’s the conflict itself. Putin’s personality arguably played a major role in Russia’s decision to intervene. And what if Zelensky, with his social media skills and personal beliefs, was not in power or had gone into exile as the invasion began (as many expected he would)? Thinking counterfactually is one way to investigate how Russia’s invasion of Ukraine could have played out very differently with different personalities in power in key states.

Counterfactual methods can also push leader personality researchers to show more precisely how specific leader characteristics affect international outcomes, moving beyond the well-established notion that different personalities behave differently in similar circumstances. Because good counterfactuals must narrowly and clearly define causal links between the counterfactual manipulation and its asserted effects, they can engage in more exacting analysis of different aspects of leader personalities. For all these reasons, it is surprising that the counterfactual method is not more widely and explicitly used in research on leaders and international relations. We hope that our research helps to change that.