The present research demonstrates rapid assimilation-the immediate integration of new information with existing beliefs. A vignette described generous and stringent welfare plans, one proposed by Democrats and one proposed by Republicans, manipulated between-subjects. Democrat and Republican participants were influenced by policy content, but also strongly influenced by the political party of the person proposing the plan. Participants underestimated the influence of party on their evaluations. Finally, the newly formed implicit evaluations mediated the effect of party information on self-reported evaluations, both immediately (Studies 1 and 2) and after a several-day delay (Study 2). The results suggest that (a) identity automatically influences evaluation separate from message content, (b) participants did not report awareness of this influence, and (c) when new information can assimilate to pre-existing social cognitions-such as one's political identity-then implicit evaluations form rapidly and show strength, durability, and predictive validity characteristic of well-elaborated evaluations.