One of the hallmarks of the 2004 presidential election was the unusual emphasis on face-to-face voter mobilization, particularly face-to-face mobilization conducted within neighborhoods or social networks. Unlike previous studies of face-to-face voter mobilization, which have focused largely on nonpartisan campaigns conducted during midterm or local elections, this study assesses the effects of a campaign organized by MoveOn.org, an organization that allied itself with the Democratic Party in 2004 to aid presidential candidate John Kerry. A regression discontinuity analysis of 46,277 voters from 13 swing states demonstrates that neighbor-to-neighbor mobilization substantially increased turnout among target voters during the 2004 presidential election. Contact with MoveOn volunteers increased turnout by approximately nine percentage-points. This finding corroborates experimental findings showing the effectiveness of door-to-door canvassing but contradicts results suggesting that such mobilization is ineffective in the context of high-salience elections.