Was Mitt Romney’s GOP convention speech a dud? That’s what a new Gallup poll appears to indicate. The just-released survey shows that Mr. Romney’s Thursday night address scored low compared with previous such speeches.

Thirty-eight percent of respondents rated Romney’s big moment as “excellent” or “good,” according to Gallup. Thirty-seven percent judged it “OK,” “poor,” or “terrible.”

That’s “the lowest rating of any of the eight speeches Gallup has tested since Bob Dole’s GOP acceptance speech in 1996,” according to Gallup editor Frank Newport.

Plus, the Republican National Convention as a whole didn’t sway many voters, according to Gallup. Forty percent of respondents said it would make them “more likely” to mark their ballots for Romney, while 38 percent said it would make them “less likely” to vote GOP.

Well, we’ve got a couple of comments here. The first is that one poll does not a trend make, even if it’s from a pollster as respected as Gallup. Other surveys indicate that Romney got at least a modest bounce out of his nominating convention in Tampa, Fla. Rasmussen Reports’ daily tracking poll now gives Romney a 48 percent to 44 percent lead over President Obama. That’s about a six-point gain for the GOP nominee over the past week.

Second, self-reported voting intentions – saying something will make you more or less likely to cast your ballot a certain way – is an imprecise measure of election outcomes. Lots of things affect an individual’s vote. In retrospect, it’s often hard to single out a particular event as the moment that pushed a voter one way or another. Events that seemed important at the time can fade by November.

Third, the real effect of the GOP convention can’t be measured until after this week’s Democratic National Convention in Charlotte, N.C. It’s possible that Mr. Obama may not get even a modest boost from the event – and it’s possible that he’ll end up with polls showing him a consensus leader.

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If the race remains roughly tied, or with only a percentage point or two separating the contenders. Romney might be able to claim that he did better out of the conventions than the incumbent did, writes New York Times polling analyst Nate Silver on Monday.

Romney’s bounce “may turn out to be ‘just fine’ once we see a few more polls, and how the numbers move after Charlotte,” writes Mr. Silver.