CQ Politics: There have been a lot of questions about the long-term implications of the “bounce” Republican presidential nominee John McCain enjoyed in the wake of the GOP’s national convention — one that erased the gains Democratic opponent Barack Obama had made with his convention a week earlier and, in some polls, have shown McCain with a small lead with just less than two months to go before the Nov. 4 election.
But an analysis of the trajectory of past post-convention bounces reveals that it’s risky to make presumptions based on the current polling numbers. The five examples laid out here, using Gallup Poll data for consistency, present a decidedly mixed bag, with the bounce beneficiaries maintaining momentum in some cases, and the bounces going flat in others.
1960: Obama supporters will like this one. Democrat John F. Kennedy had a poll lead over Republican Richard M. Nixon by 4 percentage points going into the parties’ conventions. The first poll after both conventions showed Nixon, then the incumbent vice president, ahead of Massachusetts Sen. Kennedy by 6 points, indicating a meaningful bounce in an otherwise tight contest. But Nixon’s post-convention lead dissipated to 1 point by the time of their first, historic televised debate. Kennedy walked out of that face-off with a 3-point lead. JFK held a lead in polls over Nixon throughout the rest of the campaign, though that small edge narrowed even further and he ended up winning by a margin of less than 1 percentage point in the popular vote. There's more
Here's another good read on this point.
