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Both presidential campaigns are furiously spinning the scraps of voting data that we now have -- Mitt Romney's campaign has charts showing President Obama's early edge has fallen off in Iowa, Obama's campaign has photos of long lines at polling stations in several swing states, Romney's campaign is spending money in Pennsylvania. But let's be real. The one state that really matters is Ohio. While it is mathematically possible for both candidates to win without Ohio, it is extremely unlikely. All the last-minute spinning might have left you, dear readers, in a state of confusion about what's going on there. But there's actually a lot we know. To organize our guide to what is happening in Ohio, we're going to take a page from former Secretary of Defense Donald Rumsfeld, who once famously said:

"There are known knowns; there are things we know that we know. There are known unknowns; that is to say there are things that, we now know we don't know. But there are also unknown unknowns — there are things we do not know we don't know."

Known knowns

Why Ohio must be won: The New York Times' Nate Silver's FiveThirtyEight election forecast model shows that Ohio is the state most likely to tip the electoral college vote to one candidate or the other. It holds that Romney has a 3 percent chance of winning without Ohio, while Obama has an 8 percent chance of doing so. A problem for Romney, Silver says, is that for Romney to win without Ohio, he probably needs to pick up Midwestern states that are quite similar to Ohio, like Wisconsin and Iowa. Granted, Silver damaged his credibility in the eyes of the Times public editor with a bet that demonstrated he actually believes his own forecast. But his model relies on the same polls everyone else does.

Official numbers: 1.3 million people have voted -- that's 21.8 percent of the total vote in 2008. Ohio doesn't register by party, but 30 percent of those who've voted last voted in a Democratic primary, while 24 percent last voted in a Republican one.

Polls: The major poll tracking sites all show an Obama lead in Ohio. Real Clear Politics has Obama is averaging a 2.3-point lead. Talking Points Memo's poll tracker has Obama leading 48.3 percent to 46.8 percent. The Huffinton Post's model shows Obama leading 48.5 percent to 46.1 percent. Drew Linzer's Votamatic shows Obama leading 51.6 percent to 48.4 percent, and forecasts Obama winning 52 percent to 48 percent. Perhaps more important, as you can see in the charts at left, none of these poll trackers has ever shown a Romney lead. Not after the Republican National Convention, not after Romney's great debate performance in Denver.