Impacts of Internet use on political information seeking and subsequent processes have been subject to much debate. A 2-session online field study presented online search results on political topics to examine selective exposure and its attitudinal impacts. Session 1 captured attitudes, including their accessibility. Session 2 tracked what online search results participants selected and how long they read them; participants then reported attitudes again. The study represented a 4x8x2x2 within-subjects design: 4 topics, 8 browsing intervals each, with articles presenting opposing stances, with low versus high source credibility. Attitude-consistent messages and messages from high-credibility sources were preferred. Exposure to attitude-consistent search results increased attitude accessibility and reinforced attitudes, whereas exposure to attitude-discrepant content had opposite effects, regardless of messages' source credibility.