Beyond the national horse race and Nate Silver's excellent forecasts, here are some key numbers to watch over the next few weeks.

Obama's lead among registered voters: If this number, which tends to be around 4 to 5 percent now, holds, it means that his electorate has room to grow. But if that number holds too long, it means that these potential voters are going to sit out the election.

Obama's lead among Hispanics/Hispanic enthusiasm: Right now, Obama is on track to get 7 out of every 10 voters from those who identify as Hispanic. And enthusiasm among that group, while lower than others, is sufficient to give Obama the number of voters he needs in states like Colorado and Nevada.

Mitt Romney's share of working-class white votes in the Midwestern battlegrounds: The closer Mitt Romney is to 60 percent (or more) among working-class white men, and over 55 percent of working-class white women, the closer he'll come toward blasting through Obama's firewalls.