The so-called bounce from the Democratic National Convention was par for the course for major party conventions, according to Gallup Poll results taken since 1964, the American Presidency Project reports.

Based on polls taken the Sunday before the convention and the Sunday after, the Barack Obama-led presidential ticket rose by 6 percent; the average bump since 1964 has been ... 6 percent. Not all observers agree that the bounce has been on track — Politico.com wrote yesterday that Obama's bounce was smaller than usual, but then they're using Gallup tracking polls that exceed the time span used by the APP. On Saturday, for example, Obama was up by 8 percentage points; by Monday, that had slipped to 5.

The bounce isn't guaranteed. In 2004, John Kerry saw a 1 percent decline in his ratings, and in 1972, George McGovern saw no loss and no gain in his poll numbers. On the plus side, Bill Clinton saw a 16-point bump in 1992, the highest bounce since Jimmy Carter's 10-point showing in 1980.

The good news for John McCain, currently at the Gustav-truncated GOP convention, is that Republicans have never seen a decline after their convention. Their best showings were the 8-point gains posted by Ronald Reagan in 1980 and George W. Bush in 2000.

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