Mark Bauerlein explains in The Chronicle:
The first protocol of academic society might be called the Common Assumption. The assumption is that all the strangers in the room at professional gatherings are liberals. Liberalism at humanities meetings serves the same purpose that scientific method does at science assemblies. It provides a base of accord. The Assumption proves correct often enough for it to join other forms of trust that enable collegial events. A fellowship is intimated, and members may speak their minds without worrying about justifying basic beliefs or curbing emotions….
After Nixon crushed McGovern in the 1972 election, the film critic Pauline Kael made a remark that has become a touchstone among conservatives. “I don’t know how Richard Nixon could have won,” she marveled. “I don’t know anybody who voted for him.” While the second sentence indicates the sheltered habitat of the Manhattan intellectual, the first signifies what social scientists call the False Consensus Effect. That effect occurs when people think that the collective opinion of their own group matches that of the larger population. If the members of a group reach a consensus and rarely encounter those who dispute it, they tend to believe that everybody thinks the same way….
The final social pattern is the Law of Group Polarization. That law–as Cass R. Sunstein, a professor of political science and of jurisprudence at the University of Chicago, has described–predicts that when like-minded people deliberate as an organized group, the general opinion shifts toward extreme versions of their common beliefs.