A battleground electoral primer (and a Virginia surprise)

Want to make sense of the new slew of battleground state polls coming today? Why is John McCain pulling out of Michigan - but tying Barack Obama in one Minnesota poll - a big deal? By request, here are some basics to help you sort through the electoral map.

Essentially, the race comes down to 15 states, with the others falling into solid McCain or solid Obama territory. A candidate needs 270 electoral votes to win.

Those states are: Colorado (nine electoral votes), Florida (27), Indiana (11), Iowa (7), Michigan (17), Minnesota (10), New Hampshire (4), Missouri (11), New Mexico (5), Nevada (5), North Carolina (15), Ohio (20), Pennsylvania (21), Washington (11), Wisconsin (10), and Virginia (13).

Without those states included, Obama currently leads McCain in polling 179 to 163.

Electoral observers expect Obama to win in Iowa, Washington, New Mexico and Michigan, where McCain essentially pulled out last week. That's 219 for the Democrat.

Advisers in both campaigns expect McCain to win Missouri. That's 174 for the Republican.

So - 11 states to watch. The biggest battlegrounds are Ohio and Florida, where McCain led until recently, and Pennsylvania, which Obama is leading by 6-10 points. Obama, however, struggled with Pennsylvania's rural whites in the Democratic primary, and those voters are still considered a vulnerability for him.

Obama has put several traditionally Republican states into play - most notably Virginia and North Carolina, where he leads in recent polls, and Indiana. (Update: Two new polls show a surprisingly large Obama lead in Virginia. SurveyUSA puts Obama up 53-43; Suffolk has Obama up 12.)

But polls in those states, as well as several other battlegrounds, have been volatile. Expect that to continue as October brings two more presidential debates, and much more nasty politicking.

(Or, you can just follow this: Amazon.com is keeping track of Obama and McCain masks sold for Halloween. Obama currently leads - 56-44 percent.)