Brendan Nyhan and Jacob Montgomery talk sense here. I am perhaps too influenced by Steven Rosenstone’s 1983 book, Forecasting Presidential Elections, which is the first thing I read on the topic. In any case, I agree with Nyhan and Montgomery that the difference in vote, comparing a centrist candidate to an extreme candidate, is probably on the order of 1-2%, not the 4% that has been posited by some.
