With a race this close, small but important factors will likely be key.

About 4 million more Latinos are registered to vote this year than in 2008, and Obama has the support of 69 to 70 percent of them, according to the polls -- a finding that tops his 67 percent showing in 2008. But to what extent will lower enthusiasm levels among Latinos this year offset that support? Substantially more 18-to-29-year-olds are registered voters today than were four years ago. However, in a just-released national survey conducted by Harvard University's Institute of Politics, Obama is leading by only 19 points, 55 percent to 36 percent, among likely voters in that age cohort, well behind the 66 percent he won four years ago. The Obama campaign is moving heaven and earth in the social-media sphere to try to boost his performance and the turnout among this key group, but will it work?

Although most observers expect that the Obama campaign will have an even better voter-identification and get-out-the-vote operation in 2012 than in 2008, hardly anyone has a clue about what kind of ground game the Romney campaign will mount. The remarkably effective Republican field operation in President Bush's 2004 reelection campaign was allowed to grow flaccid in intervening years; how much of it the Romney campaign has been able to replace or replicate since he nailed down the nomination in April is anyone's guess.

No doubt Republicans were kicking themselves on Wednesday morning after the second debate over how badly Romney muffed the Libya question. Obama, in one of the few selected questions of the evening that seemed designed to help Romney, had been asked about security mistakes that led to the deaths of Chris Stevens, the U.S. ambassador to Libya, and three other Americans in Benghazi. Obama ignored the question and launched into a discussion of the loss and the administration's efforts to bring to justice those who killed the four Americans. All Romney had to do was to suggest to the man who asked the question to repeat it again because apparently the president had not heard it, as he certainly didn't answer the question. Although admittedly snarky, such a move would have been devastating for the president, because he has few available answers at his disposal. Instead, Romney went off talking about what Obama said in the Rose Garden the day after the attack.

I am now reconciled to the fact that this will be a race to the wire. I am watching Ohio and a handful of other swing states that are right at, or near, the 270-electoral-vote tipping point. In the end, the odds still favor the popular and electoral vote heading in the same direction, but the chances of a split like the one in 2000 are very real, along with the distinct possibility of ambiguity and vote-counting issues once again putting the outcome in question. Ugh.