Though lightly regarded by many observers, political parties have been able to steer presidential nominations to insider favorites in all nine of the contested cases from 1980 to 2000. Democrats had more trouble in 2004, but still managed to avoid insurgent Howard Dean. This paper explains how today's presidential parties -- understood as coalitions of elected officials, interest and advocacy groups, and ideological activists -- have learned to work together in the so-called Invisible Primary to affect the outcome of the state-by-state primaries and caucuses. The paper concludes with a discussion of the influence of parties in the pre-Iowa phase of the 2008 nominations.