In the United States, Democrats and Republicans believe that members of the other party hold more extreme views than they themselves do (for example, immigration positions).
Press coverage exacerbates this impression. At the mass level people perceive greater differences between the two sides than actually exist.
People tend to overestimate how much opposing members disagree with them.
See the full study here :
Levendusky & Malhotra (2013). The Effect of “False” Polarization: Are Perceptions of Political Polarization Self-Fulfilling Prophecies?