Presidential campaign effects are small.

Paul Campos writes:

I’m certainly open to the possibility that presidential campaigns are, under contemporary political and cultural conditions, becoming significantly less effective than they were in the past.

Actually, though, the consensus is that campaign effects (for the general election for president) were small in the past too. The classic reference on this is Rosenstone (1983), where he found that election outcomes could be predicted pretty well from economic and political “fundamentals” that were not affected by campaigning. The classic case study is 1988, when Dukakis was ahead of Bush Sr., who looked like a loser in ever way, and then Bush won. The point here is that, even when Dukakis was leading, people in the poli sci community were pretty sure that Bush was going to win, because they’d read Rosenstone. Following that was our 1993 article explaining why elections were predictable even though polls were variable, which featured this table:

The big change since then is that polls are no longer variable.

Regarding 2024: I think it was well understood that campaign effects are small. But with the election forecast being so close, this is the one setting where even small effects of less than 1 percentage point could make a difference. So I think 2024 is consistent with our understanding. The most intersting issue here is the role of inflation and the economy. Arguably the Republicans did well and the Democrats did poorly in the meta-campaign of what the economy was said to be about. Yet another way of saying this is that Trump was kicked out unfairly because of covid, and then, four yers later, Biden/Harris were kicked out unfairly because of covid.