This paper examines the relationship between ideological position and electoral success in U.S. elections. We study primary and general elections to the U.S. House of Representatives over the period 1980-2010, focusing on races with no incumbent. Following previous literature, we use campaign donations to estimate the ideological positions of non-incumbent candidates. We find that in primary elections more extreme candidates receive more votes, and are more likely to win, than moderate candidates. However, the differences between extremists and moderates are small. More importantly, we show that the “reward” to extremism in the primary is swamped by an opposing reward to moderates in the general election. In general elections moderate candidates tend to receive more votes, and win more often, than extremists.