Given the fluid context of primaries and observed swings in national polls, many Democratic voters likely switched candidate support over the course of the 2008 primary campaign. We examine how perceptions of early caucus and primary outcomes subsequently affected voter choice and candidate momentum. Although the 2008 calendar left many voters with a brief window to assess candidates, it nonetheless allowed a non–front-runner to benefit from momentum and win the Democratic nomination. This article employs a panel study of voters surveyed at two time points during the nomination contest to assess individual-level change in candidate support. Results from the earlier states sent signals about candidate viability to people who had not yet voted. We find that voters deciding after results were in from early states changed their perceptions of candidate viability and that this changed whom they intended to support. We conclude that momentum remains an important factor in presidential nominations.