This article explores how exposure to ideological online news media contributes to political misperceptions. Using data from a 2012 U.S. presidential election survey (N=1,004), the study tests three forms of media effects. Panel data show that biased news use promotes inaccurate beliefs, while cross-sectional data reveal how these effects manifest. The study finds no evidence that ideological media reduce awareness of politically unfavorable evidence, though they may promote misunderstandings of it. The strongest effect is that ideological media encourage inaccurate beliefs regardless of what consumers know about the evidence. The article argues that ideological news outlets shape beliefs by altering what users know and whether their beliefs align with that knowledge. It challenges the idea that misperceptions stem from information deficits, instead suggesting they result from psychological processes. The study uses survey data to examine how ideological news influences beliefs about four political issues: Obama's birthplace, the existence of WMDs in Iraq, Romney's role in Bain Capital, and the BP oil spill's impact on marine life. Results show that ideological media use is associated with holding outlet-favored beliefs, even when users know the evidence. The study finds that ideological media use is linked to holding misperceptions about issues like the BP oil spill and Romney's role, but not about more factually clear issues like WMDs or Obama's birthplace. This suggests that the influence of ideological media varies by issue. The study also finds that ideological media use is associated with holding misperceptions regardless of users' knowledge of the evidence, indicating that beliefs can deviate from what is known. The study highlights the importance of understanding how ideological media shapes beliefs, even when users are aware of the evidence. It suggests that ideological media may promote misperceptions by influencing beliefs beyond the knowledge of the evidence. The study concludes that ideological media use has a significant impact on political beliefs, even when users are aware of the evidence, and that this effect is consistent across different issues. The study also notes the limitations of self-reported data and the need for further research to better understand the mechanisms by which ideological media influences beliefs.This article explores how exposure to ideological online news media contributes to political misperceptions. Using data from a 2012 U.S. presidential election survey (N=1,004), the study tests three forms of media effects. Panel data show that biased news use promotes inaccurate beliefs, while cross-sectional data reveal how these effects manifest. The study finds no evidence that ideological media reduce awareness of politically unfavorable evidence, though they may promote misunderstandings of it. The strongest effect is that ideological media encourage inaccurate beliefs regardless of what consumers know about the evidence. The article argues that ideological news outlets shape beliefs by altering what users know and whether their beliefs align with that knowledge. It challenges the idea that misperceptions stem from information deficits, instead suggesting they result from psychological processes. The study uses survey data to examine how ideological news influences beliefs about four political issues: Obama's birthplace, the existence of WMDs in Iraq, Romney's role in Bain Capital, and the BP oil spill's impact on marine life. Results show that ideological media use is associated with holding outlet-favored beliefs, even when users know the evidence. The study finds that ideological media use is linked to holding misperceptions about issues like the BP oil spill and Romney's role, but not about more factually clear issues like WMDs or Obama's birthplace. This suggests that the influence of ideological media varies by issue. The study also finds that ideological media use is associated with holding misperceptions regardless of users' knowledge of the evidence, indicating that beliefs can deviate from what is known. The study highlights the importance of understanding how ideological media shapes beliefs, even when users are aware of the evidence. It suggests that ideological media may promote misperceptions by influencing beliefs beyond the knowledge of the evidence. The study concludes that ideological media use has a significant impact on political beliefs, even when users are aware of the evidence, and that this effect is consistent across different issues. The study also notes the limitations of self-reported data and the need for further research to better understand the mechanisms by which ideological media influences beliefs.