Donald Trump changed the GOP. But has he weakened it?

Most voters who were Republicans—or Democrats—in 2016 have stuck with their party

One of the more famous studies in political psychology found that people will defer to their party when deciding which policy positions they do or do not support. In his aptly-titled 2003 paper “Party Over Policy,” Geoffrey Cohen writes:

Four studies demonstrated the impact of group influence on attitude change. If information about the position of their…