Unless you're David Plouffe or another member of President Barack Obama's cheerleading squad, you probably wouldn't argue that Obama won Wednesday night's debate. Indeed, instant polls from CNN and CBS showed Romney leading Obama by 42 to 22 percentage points, respectively, on the question of who won.
But can even a dominant win in a debate produce a victory in November? A few key numbers suggest that Romney supporters shouldn't expect too much as a result of last night's performance.
One of those numbers is 32. That's the percentage of undecided voters who told Washington Post and ABC News pollsters last week that they were "very interested" in the presidential debates. By contrast, 59 percent of definite Obama supporters and 53 percent of Romney supporters said they were "very interested."
As Scott Clement wrote for The Fix, "The poll’s finding underscores the challenge for Obama and Romney to sway a shrinking and elusive slice of the electorate with less than five weeks left in the contest. In addition to lacking clear support for Obama or Romney, on-the-fence voters are much less likely to say they are 'absolutely certain to vote' than those with firm opinions, even further limiting their potential impact on the election."
The narrowness and elusiveness of that slice of the electorate may explain why John Kerry's acclaimed performance in the 2004 presidential debates didn't lead to a Kerry presidency. Although Kerry gained about four points in the polls between the end of the Republican National Convention and the end of the debates, that only put him at 46 or 47 percentage points overall -- less than the 48 points that pollsters gave him at his peak in the days leading up to the convention.
In other words, it's reasonable to conclude that the debates helped Kerry earn back the votes of disaffected voters who'd previously supported him, but he didn’t appear to win over many new converts.
Romney's performance could have a similar effect on voters and donors who were losing faith in his candidacy, and that makes things much more difficult for Obama. But unless he wins the votes of either Obama's supporters or those hard-to-reach undecided voters, he'll have a hard time winning in November. Nate Cohn of The New Republic explained it this way:
To date, Romney hasn't exceeded 47 percent of the vote, and a return to that number would not give him the lead, at least without a decrease in Obama's support. Although it's possible that Romney could convince Obama supporters to join his cause, it would probably be the first instance of the debates breaking out of the prior contours of the race.