If you are looking at the national polls, you might be wondering what is going on. One poll has a fourteen percentage point lead for Obama, another has two. Gallup has experienced some noticeable tightening over the last week and has two poll models to choose from.

I think two things are going on. First, no one is sure who a “likely voter” is.  If Gallup doesn’t know which model is right, it is hard for non-pollsters to fathom. On national pollster tells me that, given the uncertainty about turnout, using “registered voters” makes as much sense as anything. And second, a lot of people are sloshing around between undecided and each of the two candidates.

Is Barack Obama ahead? Sure, but the margin isn’t clear at all. Maybe the race is all but over. Or maybe things are still in flux, made a tad more unpredictable by the public’s discovery that Obama wants to “spread the wealth” and raise taxes in a recession. (Seriously, I bet a majority of the electorate didn’t know that until the debate.) And the undecideds? A smart pollster honestly confesses: “Who knows?”

This isn’t exactly unprecedented. If you like, take a walk down memory lane and look at the October 2004 polls. The race sure did tighten — but not enough for a come-from-behind win. What makes this year so interesting is that no one is quite sure who’s going to show up — or if Joe the Plumber is the last twist in the race.