This study compares the leading primary vote forecasts for a common set of candidates and nomination campaigns, updated through 2008. Pre-primary and post–New Hampshire primary forecasts are estimated. Models that predicted well the primary vote from 1980 to 2000 produce substantial errors in prediction for the 2004 and 2008 presidential nominations. This suggests that the factors driving presidential nominations during the 1980s and 1990s are changing in ways that have increased the potency of campaign momentum in presidential nominations. Post–New Hampshire forecasts, which capture the effects of momentum from the early contests, continue to predict well candidates' primary vote shares.