From the same post:

One might expect it [our gut-feel sense] to be especially bad in the case of presidential primaries. There have been only about 15 competitive nomination contests since we began picking presidents this way in 1972. Some of them — like the nominations of George McGovern in 1972 and Jimmy Carter in 1976 — are dismissed by experts if their outcomes did not happen to agree with their paradigm of how presidents are chosen. (Another fundamental error: when you have such little data, you should almost never throw any of it out, and you should be especially wary of doing so when it happens to contradict your hypothesis.)