During an interview with MSNBC's Chris Matthews Wednesday night, Barack Obama -- a former smoker -- was asked when he had his last cigarette. "I fell off the wagon a couple times during the course of it, and then was able to get back on," Obama responded. "But it is a struggle like everything else." And now ABC News' Jake Tapper has weighed in with an example of an instance in which he was sure he'd smelled smoke on Obama. (Obama's campaign denied it.)

Now, I know what many of you are probably thinking -- what an insignificant issue, what a silly thing for anyone to focus on when determining a presidential candidate. And I agree. But.

There are, according to one poll, a surprising number of Americans who care whether their president smokes. In a 2007 poll conducted jointly by the Washington Post and ABC News, 21 percent of respondents said they would be less likely to vote for a given candidate for president solely because that candidate smoked. (By way of comparison, 58 percent said they'd be less likely to vote for someone older than 72 -- John McCain better hope that number doesn't hold up -- 26 percent said they'd be less likely to vote for someone who'd been divorced twice, and 29 percent said they'd be less likely to vote for a Mormon.) And anecdotally, I know that when I've told friends who are Obama supporters that he was until very recently a cigarette smoker, I've seen a perceptible change in them. More than one -- including one who's a smoker herself -- said it changed their opinion of him for the worse.

Like I said, this is a little thing in the grand scheme. But 21 percent of voters is not small, and I think this is an interesting reminder of how what may seem to many of us the tiniest of issues (Al Gore's wardrobe, John Kerry's choice of outdoor recreation, whether George W. Bush would be a good drinking buddy) have the potential to make a big impact in a presidential race.