While a lot of focus has been put on the national poll numbers, which point to a close race, elections are won and lost based on electoral votes. Though Barack Obama and John McCain are essentially tied in most national polls, when you analyze the race on a state-by-state basis, it’s easy to see why McCain considers himself the underdog.

Looking at Real Clear Politics polling averages, I see that 18 states are currently within the single digits. Of those states, Obama has an edge in 11 to McCain’s 7. To be fair, in many of those states Obama’s edge is statistically insignificant. But far more troubling for McCain is the fact that Bush carried 12 of these 18 states. This means that Obama is putting far more 2004 red states in play than McCain is putting blue states in play. Or to express it another way, McCain will be defending a lot more turf this fall, and thus will be more limited in his ability to go on offense.

Obama is competitive in several states that are usually reliably Republican. In Virginia, which hasn’t voted for the Democrat since LBJ’s 1964 landslide, Obama is essentially tied as he is in Indiana, which Bush won by 21 points in 2004. In North Carolina, McCain’s average lead is 3.5 percent, but Bush won there by 12 points in 2004 — even though pre-scandal North Carolina Senator John Edwards was on the opposing ticket. In Iowa, which Bush lost to Gore but won narrowly against Kerry, Obama has a 5.7 point lead. Obama campaigned hard in Iowa all of last year in the run up to his launch pad victory in the caucuses, while McCain largely wrote off the state. I don’t know anybody who thinks McCain is going to win the state’s 7 electoral votes. In New Mexico, which Gore won but Bush carried in 2004, Obama has a 6-point lead in the latest poll. He also has a pickup opportunity in Colorado and Nevada, which have been trending Democratic.

The fact that McCain is keeping things close in such an unfavorable electoral environment for Republicans certainly says something. But it’s worth noting that of the six Kerry states in which McCain is within the single digits, all of them are states that have been battlegrounds in recent elections anyway. Unlike Obama, he isn’t putting long-time Democratic strongholds in play (i.e. California, New Jersey, etc). Michigan, New Hampshire, Wisconsin, Minnesota, Oregon, and Pennsylvania may be close, but that’s generally to be expected. Of those six states, I would say that New Hampshire and Michigan present McCain with the best opportunity for pickups, while the other four states are a stretch.

While we can drive ourselves crazy doing the electoral math between now and Election Day, here’s the bottom line. In 2004, Democrats had a much worse candidate, and the electoral environment was much more favorable for Republicans, and yet Kerry fell just 18 electoral votes shy of becoming president. Looking at the election on a state-by-state basis, you can come up with a lot of scenarios whereby Obama gets to 270 electoral votes, but it’s a lot harder to come up with a combination of states that will put McCain over the top. This isn’t to say it can’t be done, but amid all of the focus on the closeness of the daily national tracking numbers, it’s important to keep in mind what an uphill climb this still is for McCain.