Studies on retrospective voting argue that voters under presidentialism tend to assign co-responsibility for the president’s performance to her party in congressional elections. However, it is not uncommon for presidential parties to distance themselves from an unpopular president or for opposition parties to cooperate with a popular president. In doing so, parties can signal to voters that they side with a popular (or against an unpopular) president. Yet little is known about whether this strategic behavior has electoral payoffs. This study proposes a popularity-response model, where parties’ electoral outcomes are a product of how they respond to public opinion on the president. I hypothesize that parties defecting from an unpopular president (or cooperating with a popular president) minimize electoral losses and obtain a further electoral boost. Analysis using an original dataset coding issue congruence between presidents and parties prior to 35 elections in 18 Latin American countries supports this claim.