German Chancellor Angela Merkel’s comment on Sunday that Europe could no longer fully rely on the United States as an ally raised alarm in foreign policy circles. America’s commitment to defend Western Europe through the North Atlantic Treaty Organization has been a cornerstone of policy since World War II. The U.S.-German partnership has been a pillar of a stable, democratic and prosperous Europe.

That the election of Donald Trump could put those bonds in doubt was understandably surprising.

But it’s not just because of President Trump.

Merkel’s comments have highlighted a deeper question: Can a democracy like the United States still make commitments that are likely to outlast the turnover of its leaders?  The answer affects U.S. foreign policy not only during the Trump administration, but after Trump is gone.

Democracies have been seen as durable allies, even though their leaders change frequently


The hands of Indian Prime Minister Narendra Modi and German Chancellor Angela Merkel during their news conference in Berlin. (AFP/Getty Images)

It was not always obvious that an alliance among democratic countries would be durable. A long-standing tradition in international relationship scholarship was skepticism that democratic governments could sustain consistent foreign policy commitments over time. Electoral turnover and volatile publics meant that any promise made by one leader could be abandoned by the next.

In the 1990s, however, a consensus emerged among scholars that democratic countries, rather than being fickle partners, were actually quite good at making durable commitments. A 1996 article by Kurt Taylor Gaubatz found that alliances among democratic states lasted longer on average than alliances that include non-democracies.  In a 2009 article, Brett Ashley Leeds, Michaela Mattes and Jeremy S. Vogel looked at how leadership turnover affects whether a country comes to the defense of an ally in wartime. They found that leaders in general were less likely to honor a treaty if there had been turnover in their base of support since the leader who had originally signed the agreement. However, the effects of such turnover disappeared when looking only at democracies.  That is, commitments made by democratic leaders were quite likely to be honored by their successors.

Why might this be?

The first reason why democratic countries are more likely to live up to their commitments is that they are more careful about making promises in the first place. Democratic governments tend to commit to policies that enjoy support across the political spectrum.  For example, the requirement that two-thirds of the Senate is needed to ratify a treaty means that only treaties that enjoy bipartisan backing can clear the hurdle.

Second, while leaders change regularly in democracies, they also have institutions, such as electoral competition and institutional checks on the government’s power, that make leadership changes less consequential. Different leaders have to appeal to the same electorate and compete for swing voters in the middle of the political spectrum. While this dynamic does not make parties identical, it keeps them from pulling too far apart, for fear that they will lose voters. Once in power, the individual leader cannot make decisions unilaterally but has to consult with other political actors, such as the legislature or other political parties in a coalition. These forces prevent wild policy swings.

In contrast, authoritarian states can experience long periods of stability while a particular ruler is in power, but they are also prone to dramatic changes when a leader is ousted or dies. The 1959 revolution in Cuba turned that country from a U.S. ally into a communist threat. The 1979 revolution in Iran replaced the pro-America shah with an Islamic government that has been a regional adversary ever since. Absent a major change in the international environment, comparable swings in democratic foreign policy are unlikely.

Finally, democratic governments provide many channels through which outside actors can access the political process, whether that be through a government agency, the legislature or by direct appeals to the public. This creates opportunities for allied states to influence decision making and ensure that commitments are adhered to. For example, Israel has benefited from public relations and lobbying efforts that have built high levels of support within Congress and the public. This supports ensures that American policy is broadly supportive of Israel even as individual presidents come and go.

The factors that make democratic alliance commitments more stable are eroding in the United States

What we are now learning, however, is that all of these mechanisms are potentially undermined by two major trends in American politics: centralization of authority in the president and polarization of party positions.

The growing power of the presidency has been a consistent feature of post-World War II American foreign policy. But it has accelerated in recent years.

The weakening of congressional control over war powers — exemplified by the lack of explicit authorization for current military operations in Syria — has often been noted. The U.S. approach to international agreements is developing in similar ways. It is increasingly hard for presidents to get support for international treaties in the Senate. Thus, presidents have sidestepped Congress by resorting to executive agreements, which require only a presidential signature to come into force. President Barack Obama chose this option for the Paris agreement on climate change and the 2015 deal with Iran over its nuclear program.

It is easier for the United States to enter these agreements, because they do not require broad political support. But they can be exited just as easily. Specifically, executive agreements can be “unsigned” unilaterally by any subsequent president, as Trump has threatened to do.

At the same time, the parties have become increasingly polarized on almost every issue. Foreign policy has not been immune. Since World War II, there was a broad consensus that the United States was better off being actively engaged with the world through alliances, international organizations and free trade. On the surface, this consensus still holds among the American public, as bipartisan majorities say that they want the United States to play an active role in the world and support maintaining NATO.

But Trump has tapped a rich vein of public opinion that sees engagement in the world as a raw deal for Americans, who subsidize the security of other countries and lose jobs to foreign imports and immigrants. He showed that a Republican could win running on an “America First” platform.

Moreover, Trump is not just responding to this view of the world; he is also encouraging it. Polls have shown that, among Republicans, long-standing attitudes on trade and Russia have shifted dramatically, a development that is not surprising in light of political science research showing that people tend to follow cues from their party leaders.

Finally, in addition to these two trends, the 2016 election showed that it is not just allies who can take advantage of the many channels of access into the U.S. political system. We do not yet fully know how much Russia used hacked documents and misinformation to bolster the chances of the candidate more closely aligned to its interests, but we can reasonably suspect that it played a role in an otherwise close election.

U.S. commitments are likely to be weaker even after Trump is gone

What this all means is that the factors that international relationship scholars identify as sources of continuity in democratic foreign policy are eroding in the United States. Weaker institutional checks on the president and greater distance between the parties mean that bigger swings in American foreign policy are more likely in the future.

This is a disturbing development for allies hoping to make long-term defense plans based on expectations of U.S. support. And it is one that it is not likely to disappear once Trump leaves office.

Kenneth Schultz (@kschultz3580) is professor of political science at Stanford University.