While Mitt Romney continues his week-long lead in the national polls, the polls in various swing states are see-sawing back and forth in a frantic dance.
That makes predicting the outcome of the presidential race much more difficult, but those polls are likely more important when attempting to get a clear picture of how the race actually stands at the moment.
Due to the quirky math of the Electoral College, whichever candidate wins a particular state receives all of its electoral votes. Most states will definitely go to one candidate or the other, which makes states that might swing either way the most important in determining the winner of the election.
According to most estimates, President Obama can count on 201 electoral votes from safely Democratic states. Republican challenger Mitt Romney has 191, with 146 electoral votes in 11 states up for grabs.
A total of 270 electoral votes are required to win the election.
While it's possible for the candidates to tie in electoral votes, it's highly unlikely this year. It's also possible for one candidate to win the popular vote nationwide but still lose in the Electoral College and therefore lose the election.
That result is also highly unlikely, but it happened as recently as 2000, when George W. Bush lost the popular vote to Al Gore but won Florida and its (at the time) 25 electoral votes.
This year, Florida has 29 electoral votes but is likely to play a smaller role in the final decision. That dubious award goes to Ohio, which FiveThirtyEight predicts has a better than 40 percent chance of casting the deciding vote for president.
In several simulations, Obama comes 17 votes shy of winning the election outright. If he can secure Ohio's 18 electoral votes, he wins. Romney has only a few paths to the presidency without Ohio, and they are all more difficult.
Currently, Romney is ahead in Florida, North Carolina and Virginia, which would give him 248 electoral votes, 22 shy of winning.
Without Ohio, he would need Colorado, Iowa and New Hampshire, all of which are doable for him, but he would still be short 4 votes, requiring a pickup in Michigan, Nevada, Pennsylvania or Wisconsin, all of which Obama currently leads in.
But with Ohio, Romney need only take one of Colorado, Iowa or New Hampshire, a likely scenario.
For his part, Obama seems poised to take Pennsylvania, Michigan, Wisconsin and Nevada for another 52 electoral votes, leaving him 17 short.
Even without Ohio, he can take Florida and win, or either North Carolina or Virginia plus any other small state.
Any combination of three small states would also get him to 270.
Which is why the candidates have been pouring time, energy and money into Ohio. Romney spent five days last week in the state, and the two campaigns combined have spent $93 million in advertising in Ohio.
So while Obama may be trailing in many polls, it is the swing states that count, and his more favorable positioning still leaves him just shy of a two-thirds chance to win in November.
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