Americans vote party lines; nothing predicts election outcomes as well. People may vote party lines because party candidates have views that accurately reflect the positions of their members, because party identification acts as a convenient cue that eliminates the need for greater information search or cognitive processing, or because party classification biases interpretation of other information people have about the candidates. To investigate these competing hypotheses for party effects on voter decision making, participants were presented with a choice between 2 candidates whose policy positions were more inconsistent than consistent with their party identification (Study l), or completely inconsistent with their party identification (Study 2). People voted as a function of party label in Study I, but issue stand emerged as a stronger predictor in Study 2 (although Democrats were more likely to cross party lines than Republicans). These results suggest that party identification influences how other information about the candidate is perceived and processed. Theoretical and practical implications are discussed.