The growth of partisan news sources has raised concerns that people will increasingly select attitude-consistent information, which might lead to increasing political polarization. Thus far, there is limited research on the long-term mutual influences between selective exposure and political attitudes. To remedy this, this study investigates the reciprocal influences between selective exposure and political attitudes over several years, using a three-wave panel survey conducted in Sweden during 2014–2016. More specifically, we analyse how ideological selective exposure to both traditional and online news media influences citizens’ ideological leaning. Findings suggest that (1) people seek-out ideologically consistent print news and online news and (2) such attitude- consistent news exposure reinforces citizens’ ideological leaning over time. In practice, however, such reinforcement effects are hampered by (3) relatively low overall ideological selective exposure and a (4) significant degree of cross-cutting news exposure online. These findings are discussed in light of selective exposure theory and the reinforcing spirals model.