The Obama administration’s initial ambivalence toward democratic revolutions in Tunisia and Egypt in 2011 points to a central puzzle in US foreign policy. In some countries, during some periods, America promotes liberal democracy; in other countries and periods, it tolerates or even supports authoritarianism. Why the variation? We focus on discrete decisions by a US President to retain a dictator or instead press for democracy in a client state S. Two conditions must be satisfied for a President to do the latter. (1) An exogenous domestic crisis must threaten S’s authoritarian regime. (2) The US domestic model of free-market liberal democracy must face no credible alternative in S’s region as a route to national development and security. A credible alternative model (e.g. communism or Islamism) threatens US interests by making dissenting elites in S more hostile to US hegemony and more accepting of the hegemony of America’s security rivals; that in turn makes free elections in S riskier for Washington. But when conditions (1) and (2) coincide, a new bargain emerges: S’s elites, now assenting to the US model, pledge to participate in the US-sponsored regional order, and Washington presses S’s regime into democratizing. We test our argument against two cases involving relations between the US and the Philippines, an authoritarian client until 1986. In a 1978 crisis, communism’s high credibility in Southeast Asia forced Jimmy Carter to continue supporting the Marcos dictatorship. In a 1985–86 crisis, communism’s lack of credibility allowed Ronald Reagan to drop Marcos and permit democracy.