President Obama's convention 'bounce': Is it already starting to fade?

Polls suggested that President Obama got a bigger surge in support after his convention than did Mitt Romney. But some new polls show that the bounce is coming back to earth.

Is President Obama’s post-convention bounce upward in the polls beginning to come down? We won’t know the definitive answer to that question for a few days yet, when more polls have published their latest results. But there’s at least one data point that shows Obama’s numbers returning to earth.

Rasmussen Reports’ tracking poll for Sept. 11 shows Mr. Obama leading Mitt Romney by 3 percentage points, 48 to 45. That’s down from a 5 percentage point lead on Sept. 10.

“Today’s data suggests that the president’s convention bounce has started to fade,” concludes Rasmussen in Tuesday's analysis.

Again, this is just one survey. Polls are bouncing all over the place at the moment due to the events of the Republican and Democratic conventions. Tuesday's RealClearPolitics rolling average of major surveys actually has Obama up a tick, to a 3.1 percentage point lead from Sept. 10’s 2.9.

But other individual polls are showing hints that Obama’s momentum is slowing, or that his bounce wasn’t as big as other surveys indicate.

A TIPP/Investor’s Business Daily/Christian Science Monitor poll released on Sept. 10 has Obama up by 2 percentage points, 46 to 44, among registered voters. And a new Washington Post/ABC News poll puts the presidential contenders in a virtual dead heat among likely voters, with Obama at 49 percent and Mr. Romney at 48 percent.

When all polls are taken into account, it still seems as if Obama may have received more of a boost from his convention than did Romney. But the gain may not be the game-changer that some early figures indicated.

“Seems like we’re transitioning from will-Obama-gain-any-more-ground mode to will-he-keep-what-he-got mode,” tweeted New York Times polling analyst Nate Silver this morning.

Given that, Obama’s chance of victory actually declined overnight in Mr. Silver’s election forecasting model at his FiveThirtyEight blog. It is still high, however: The model puts the incumbent US chief executive’s reelection chances at 79.8 percent.

If Obama’s bounce is indeed fading, that would not count as a surprise. There’s a reason the word pollsters use in this context is “bounce,” instead of “gain.” Bounces go up and come down. Monday, Romney pollster Neil Newhouse released a memo that dismissed convention bounces as a “sugar high” that some voters feel in the wake of their party’s quadrennial confab. His analysis here may yet prove right.

It may be next week, or even later, until the numbers calm down and stability returns to polls. (Stability, in this case, means their trends may generally mirror each other, whether the numbers do or not.) Then we can all get ready for the next big campaign event: the first presidential debate, on Oct. 3 at the University of Denver.