Post-Convention Bounce? Advantage, Obama

President Barack Obama is enjoying at least a 4 percentage-point boost among likely voters following the Democratic National Convention, which culminated with his speech accepting his party's nomination for a second term. Support for Mitt Romney has slipped.

See also:

• Republican National Convention Speakers
• Who Pays for Political Conventions?
• Historic Post-Convention Bounces

The post-convention survey, conducted by CNN/ORC International, found 52 percent of likely voters supporting Obama immediately following his party's national convention in early September. Just before the convention, held in Charlotte, N.C., 48 percent said they were backing the president.

The poll survey 709 voters who said they are likely to vote in the Nov. 6 election and has a margin of error of +/- 3.5 percentage points.

A separate poll, conducted by the Gallup organization, indicated Obama received a 5 percentage-point boost.

Romney, by contrast, saw his support drop by 2 percentage points following the Democratic convention, to 46 percent, in the CNN poll. He did not experience a significant bounce in support following the Republican National Convention, held in Tampa, Fla., in late August.

As we've pointed out before, presidential candidates have seen, on average, a 6-point bump in the polls immediately following their party's national conventions since 1964, according to the Gallup organization. The median bump is 5 percentage points.

Veteran political observers generally agree that the Democratic National Convention was more successful in boosting its party's candidate than was the Republican National Convention.

"The Democrats had a good convention, one clearly reflected in a respectable post-convention bounce - the Republicans, not so much," wrote G. Terry Madonna and Michael Young, two political scientists based in Pennsylvania. "Not that the GOP had a really bad or a dreadful convention. In truth, it had its moments. As conventions go, however, mediocre would describe it best. It wasn't the worst and certainly wasn't the best."

Madonna and Young argue that national conventions often have the same impact on a president's campaign as does his choice of vice president.

"'Bad' ones can inflict serious, sometimes fatal, damage on a party and its presidential aspirants," they wrote. "But 'good' ones seem to matter much less in terms of their ultimate impact on the November election."

Obama's post-convention bounce could be an exception. We'll find out in less than two months.

[Photo: President Barack Obama accepts the Democratic presidential nomination in Charlotte, N.C., in September 2012. Getty Images News.]

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