Novel national survey data (spanning eight years), a parsimonious definition of identity, and a new Implicit Association Test are brought together to examine "implicit party identity" for the first time. This offers the most direct evidence available that voters associate themselves with their party at a visceral level, sometimes in a more or less pronounced way than they realize or report. This pre-introspection, automatic association relates strongly to voter evaluation and interpretation of the political world. Comparisons with standard explicit measures and three key outcomes (affect, differential evaluation, and motivated processing) offer insight regarding the nature, distribution, and measurement of party identification. Explicit and implicit measures largely corroborate each other in distinguishing between Democrats, Republicans, and Independents but deviate in registering partisan intensity. "Leaners" appear closer to partisans than to pure independents, and implicit identity yields a more graduated relationship than explicit party identification with outcomes of political cognition.