A mathematical function for belief trajectories in response to a series of negative incongruent pieces of information was proposed based on the sequential information integration model (SIIM), and the function was tested in two studies. In Study 1 (N = 167), political candidates’ party affiliation information was given for initial candidate evaluation, and then belief change over time (11 times) in response to a series of negative incongruent information about the candidates was observed. Consistent with the hypothesized mathematical function, in both studies belief trajectories monotonically decreased. In Study 2 (N = 177), negative incongruent information regarding candidates caused a greater over-time decline in candidate evaluation for those who did not receive initial issue-position information than for those who did receive initial issue-position information, and a greater over-time decline in candidate evaluation for those with weak party identification than for those with strong party identification was observed.