Well, here we are. It's show time. I will shortly hazard a guess about the election results, but, first, it's important to review some of the mystery factors that might prove crucial tomorrow.

Basically, there are things we do not know. Or, in the immortal words of Donald Rumsfeld, as he jazz-riffed back in 2002 about what a war in Iraq might look like, "There are known knowns. There are things we know we know. We also know there are known unknowns. That is to say, we know there are some things we do not know. But there are also unknown unknowns, the ones we don't know we don't know."

I would suggest that Donald Rumsfeld is one of the big reasons why the Bush administration is held in such low regard today, and I would further suggest that Rumsfeld's former boss is one of the big reasons why John McCain seems destined for defeat tomorrow. Indeed, the final Quinnipiac University survey of Ohio voters, released this morning, reports that the Bush baggage is a key factor in Barack Obama's seven-point statewide lead; 69 percent of Ohioans view Bush unfavorably. And even though a plurality of Ohioans are turned off to Sarah Palin, a landslide majority considers Bush, not Palin, to be the biggest drag on McCain's prospects. In short, I'm focused on Ohio. No Republican has ever won the presidency without winning Ohio.

But I digress. In the spirit of Rumsfeld, here are some of the known unknowns:

1. Will the election-day voters cancel out the early voters? In translation, have Obama's most diehard fans already voted, only to be trumped tomorrow by the folks casting ballots for McCain? Or are Obama's gaudy early-voting numbers merely a portent of a decisive victory?

The final CBS News poll reports that, among those who have already voted (in the 36 states that offer the option), Obama is shellacking McCain by 19 percentage points. Last week, the Pew Research Center poll reported that early voters have been favoring Obama over McCain...again, by 19 percentage points. And the early-voting statistics in battleground red states also suggest a clear Obama advantage. For instance: In Florida, more Democrats than Republicans have voted early, a stark reversal from 2004; in Nevada's populous, pivotal Clark County (home of Las Vegas), early-voting Democrats outnumber their Republican counterparts by 22 percentage points; in North Carolina, the Democratic edge is 21 percentage points (up from 11 points in 2004).

These stats, and others, are not surprising, given the polling evidence that Obama voters are generally more stoked by this election than McCain voters (Gallup, mid-October: 74 percent of Obama voters said they're more enthusiastic about '08 than about previous elections; only 48 percent of McCain voters said the same). It also appears that 30 percent of all 2008 voters will have cast their ballots early. So the big question is, will there be enough McCain supporters on election day to trump the early-voting gap...or will Obama's election-day turnout operation successfully mirror what his campaign appears to have achieved during the preliminaries?

2. Will the undecideds break heavily for McCain, in sufficient numbers to erase Obama's polling lead? It is easy to goof on the undecideds - Bill Maher refers to them as "the retarded" - because, after all, how could anybody be wavering at this point, after two years of campaigning by two such starkly different candidates? But, to give them their due, many of the undecideds seem to be busy, distracted people who are honestly torn (for instance, many don't like McCain's ties to Bush, but they're wary of Obama's relatively thin resume). Pollsters say that the undecideds are older, less educated, and less affluent than the average American. They are also overwhelmingly female.

It is tempting to suggest that, nationwide, they won't make much of a difference in the end, even if they broke for McCain tomorrow by a margin of 9-1, simply because they are not sufficiently numerous. And many might simply decide to stay home. But they could still make a difference in individual states - for instance, Missouri and Florida, both of which appear to be very tight. On Wednesday, presumably, this factor will become a known known, when we check the exit polls in key states and determine the sentiments of those who made up their minds on the final day.

3. What about that "Bradley effect," anyway? We're all tired of hearing about this one. Is there a hidden racist vote that will topple Obama, or not? The McCain people are still banking on that possibility in Pennsylvania - in the hills and small towns and south Philly wards; indeed, Pennsylvania is the only major blue state that they have seriously sought to contest during the closing weeks. 

But unless millions of people are lying, the polls do not suggest a mass racist impulse. For example, the final Quinnipiac survey in Pennsylvania reports that Obama will draw 47 percent of the white vote (equaling McCain's share), and the final Ohio survey shows him drawing 45 percent of whites. Nationwide, in last week's New York Times/CBS poll, Obama drew 44 percent of whites - and that's actually a higher share of whites than Bill Clinton scored in either of his election victories, in 1992 and 1996. If Obama winds up with a white share in the mid-40s, he will have written a new chapter in American race relations.

4. Will the Hispanic electorate lose its label as "The Sleeping Giant?" Due to the oversaturated coverage of white working-class voters, Hispanics have been overlooked this year. They are members of the fastest-growing electorate, with a potentially pivotal presence in a number of battleground states, but they have long been dismissed as slumbering because their voting participation has long lagged behind their numbers. Tomorrow could be different. And even if their vote totals are no greater than in previous years, their expected overwhelming support for Obama (which few could have foreseen last winter) could be crucial factors in the red-state battlegrounds of New Mexico, Nevada, and Colorado.

There was much talk nine months ago that Hispanics would not support a black candidate, due to longstanding ethnic tensions. But that was back when Obama was paired in the Democratic primaries against Hillary Clinton, who (along with her husband) was far better known among Hispanics. The choice now, however, is between Obama (who is viewed by Hispanics, just as he is by most other demographic cohorts, as better able to handle the economy) and McCain (who once championed immigration reform, until he sold out to the right wing of his party). Obama is now expected to receive roughly 70 percent of the Hispanic vote nationwide (that would be 10 points greater than John Kerry's share); strong margins in the aforementioned western red states could make a major difference in the national outcome.

So I'll make a guess. It is bound to be wrong:

Obama, 311 electoral votes (the 252 Kerry EVs, plus Colorado, New Mexico, Iowa, Nevada, Virginia, and Ohio); McCain, 227.

Obama, 51.5 percent of the popular vote; McCain, 46.2.

By the way, here is my favorite prediction of all time: Eight years ago, on the eve of the Bush-Gore election, at the Union League in Philadelphia, I was on a panel with a colleague. In the closing moments, the moderator asked us to predict the winner. My colleague picked Gore. I picked Bush.

And the beauty of it was...we were both right.

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Programming note: I'm scheduled to be a guest tonight on Charlie Rose's PBS show. It's his election eve roundup. The other (better known) guests are Washington political analyst Charlie Cook and New York Times Magazine political writer Matt Bai.