Strategic alliances: Red, green, or “watermelon” candidates in Mexican legislative elections

What role do small parties play in new democracies? Although some research has posited that these parties developed to promote policies that the major parties were not addressing, we argue that they are as opportunistic as their larger party competitors. To test our argument, we examine the legislative electoral alliances between the Institutional Revolutionary Party (PRI) and the Ecological Green Party of Mexico (PVEM) in single member districts from 2006 to 2015. In alliance districts, the parties distribute the districts between them: those in which the candidate is from the PRI and those in which the candidate is from the PVEM. There is then a second dynamic in these electoral alliances: Many of the PVEM candidates are former PRI politicians, whom we refer to as “watermelon” candidates, as they are green on the outside and red on the inside. We argue that the parties will select the alliance strategy that will be most electorally beneficial—running a PRI, PVEM, or watermelon candidate. We find that running a PRI or watermelon candidate increases the alliance’s probability of winning. Our findings have important implications for understanding Mexican party politics as well as the role of small parties and party competition in developing democracies.