It's hard to win without a convention bounce

Some Democratic nominees got bigger bounces than any Republican — Clinton, Jimmy Carter in both 1976, when he was a fresh face, and 1980, when he faced a challenge from Edward Kennedy, and Walter Mondale in 1984…

Incumbents get about the same lift as nonincumbents’ bounces, but the latter vary more. Some new faces go over well, while others thud.

Is there a correlation between the size of the bounce and the vote in November? Certainly there was for Clinton in 1992, and the no-bounce Democrats — McGovern and Kerry — both lost. But in five of the 12 races since 1964, the loser had the larger bounce.

Will Romney get a bounce? By this time next week, we’ll see, but more important is whether he can hold on to most of it until Nov. 6.