Chapter 5 tests whether legislators are accurate in their belief that primary voters are likely to punish them for compromising. Results from a survey experiment suggest that most voters, even most primary voters, reward legislators for making compromises. However, co-partisan primary voters who oppose compromise on a specific issue are willing to punish legislators who vote for the compromise. Although legislators may benefit electorally from supporting compromise, especially in the general election, they have reason to be cautious on compromise bills to avoid voter backlash from subsets of the politically active primary electorate. Just because the subset of voters who punish legislators for compromising is small does not mean it cannot be consequential – a small subset can mobilize a strong challenger, paint a legislators’ behavior as problematic in the eyes of less informed voters, or vote on the basis of a single important vote. Moreover, across many compromise votes a legislator may face, the small groups of voters who oppose each compromise might, when added together, represent a decisive portion of the primary electorate.