Did the losing party over perform or under perform electorally in each election

[Peanut]

In '68 the Dems overperformed, Humphrey shouldn't have made it that close, with the war and LBJ.
In '72 they underperforned but it was mainly in nominating McGovern and with Eagleton.
In '76 Carter should've won 400+ EVs.
In '88 we should've won much more, if not the election.
In '08, the GOP overperformed, Obama should have won around 400 EVs with the economy as it was.
The rest were pretty much what could be expected.