Presidential elections are conducted in two stages. The November general election is proceeded by a series of contests where delegates are selected to national party conventions, which is where the parties select their candidates for the fall election. These nominating contests’ political environments vary: the rules regarding who can participate; the levels of electoral competition, which are related to when they are held; and that other offices present on the ballot, if any. We explore the effects of these conditions on voter participation in recent presidential contests and generally find turnout highest in competitive and inclusive contests where other offices are on the ballot. Examining the 2008 American National Election Panel Study, we find primary voters are more ideologically extreme than general election voters, but there is little difference between voters in closed and open primary states. We suggest primary type has little effect on the ideological composition of the electorate because modern nomination contests are low turnout elections that draw only the most politically interested.