Obama Will Get No Post-Denver Polling Bounce

In 1992, Bill Clinton enjoyed a 16 percentage-point bounce in public opinion following that year's Democratic National Convention.

Since then, the average post-convention bounce has been 5 points. Yet, because of the tightly aligned convention dates for the Democrats and Republicans this summer, as well as the expectation that John McCain will announce his running mate simultaneously with Barack Obama's acceptance speech, Democratic chances for a substantial boost in post-Denver public opinion look poor. Gallup reports:

The conventions are one of the most anticipated events of the political calendar, and thus, their potential to shift voter preferences is great. In 1988 and 1992, the conventions were the turning points in the campaign, moving the formerly trailing candidate ahead for the duration. In other years, such as 1980 and 2000, the conventions produced a change in the front-runner, but not a permanent one, as subsequent events (in particular, the debates) led to changes later in the campaign.

Typically, Gallup finds candidates gaining 5 points in the polls after their conventions, though it is far from a guarantee that the candidates will receive bounces of that size in 2008.

There are a number of factors that could lead to smaller-than-usual convention bounces this year, most notably the tightly compressed convention schedule, with the GOP Convention beginning just four days after the Democratic Convention ends. Also, it is rumored that McCain will announce his vice presidential running mate the day after the Democratic Convention ends, stealing away some of the political spotlight from Obama the day after he gives his presidential nomination acceptance speech. Lastly, the high level of early voter attention may also reduce the potential for significant shifts in voter preferences after the conventions.

More troublesome, Obama's polling numbers have declined amid a series of campaign missteps which have shifted the presidential horse race to McCain's advantage.

In the wake of the Saddleback civil forum, the Obama camp has seen a 15-point collapse in the Zogby poll, which while unusually large, is not too distinct from Obama's decline since late-July, when a the Wall Street Journal found Obama leading McCain by a 47-to -41 percent margin. The Journal survey, however, found McCain with an 11-point advantage on questions of experience and traditional values, a division that may well be exacerbated by this week's revelations on Obama's abortion extremism.

Moreover, Americans continue to harbor doubts about Obama's patriotism, which may add to the Illinois Senator's post-convention doldrums.

In the absence of a "comeback kid" moment for Barack Obama, there may be little hope for a reprise of the Bill Clinton post-convention bounce of 1992.