The conventional wisdom, which I share, is that Barack Obama will win this election, perhaps by a healthy margin. But Democrats are nervous wrecks; they're having nightmares that defeat will be snatched from the jaws of victory.
To add to their misery (and guard against complacency), here's how that horror film could play out:
In the end, the problem was the LIVs. That's short for "low-information voters", the three-fifths of the electorate that shows up once every four years to vote for president but mostly hates politics.
These are the 75 million folks who didn't vote in the primaries. They don't read news magazines or newspapers, don't watch any cable news and don't cast their ballots early. Their allegiance to a candidate is as easily shed as a T-shirt.
Several million moved to Obama through September and October; they'd heard he handled himself well in the debates. Then, in the last week, the LIVs swung back to the default choice: John McCain.
Some had good reasons other than the colour of Obama's skin to desert him; many more did not.
In October, a study by the Associated Press estimated that Obama's race would cost him 6%. The percentage was smaller, but still enough to give the presidency to McCain.
Obama's field organisation was superb, so it was no surprise that most of the 18 million Hillary Clinton voters came home to the Democrats; the person-to-person voter contact (and significant resentment about the selection of Sarah Palin) made a big difference.
But the huge swathe of more than 30 million independents broke heavily for McCain. By piling up overwhelming margins in big blue states like California, New York and Illinois, Obama carried the popular vote, but he ended up like Al Gore in 2000 - denied admission to the Electoral College.
The first ominous sign was largely missed amid the Democratic euphoria after Obama outclassed McCain on the financial crisis.
While most of the country moved toward the Democratic nominee in early October, Ohio did not. Obama could never close the sale there. In a repeat of the Democratic primary, his big totals coming out of Cuyahoga County (Cleveland) weren't enough to offset larger-than-expected losses in the suburbs around Cincinnati and Columbus.
Florida had looked promising for Obama for a time, but his weakness among seniors caught up with him. One national poll from early October should have been a warning: it showed him up by 7% overall, but down 14% among those older than 65.
And Sarah Silverman's "Great Schlep" fell short. Obama easily carried the Jewish vote, but not with the 75% won by Gore and John Kerry. As it turned out, the real problem wasn't south Florida, where Hispanics came in surprisingly well for Obama. It was erosion in the critical I-4 corridor near Tampa and in the Panhandle, where the astonishing Republican margins among whites could be attributed only to race.
Obama shifted New Mexico, Iowa and Nevada from red to blue. But there was a reason Virginia hadn't gone Democratic since 1964. The transformation of the northern part of the state couldn't overcome a huge McCain margin among whites farther south. They weren't the racists of their parents' generation, but they weren't quite ready to vote for the unthinkable, either.
As McCain closed the gap in the last week with his message on taxes and fear of another terrorist attack, the race came down to New Hampshire (which went for Kerry in 2004) and Colorado (which went for President Bush). Obama needed one of them to get to 270 electoral votes.
New Hampshire's fabled independents had long had a soft spot for McCain in GOP primaries, and they delivered for him again. Colorado, after flirting with Obama, simply reverted to form, with Palin's frontier image helping a bit.
Obama had wired every college campus in the country, and he enjoyed great enthusiasm among politically engaged young people. But less-engaged students told reporters the day after the election that they had meant to vote for Obama but were "too busy".
History held: young people once again voted in lower percentages than their elders. Waiting for them turned out to be like waiting for Godot.
The Obama margin among young voters was underestimated a little in some polls because so many 18- to 24-year-olds use only cell phones.
John McCain will make a fine president, but Republicans are subdued...
But the deeper failure of the polling came from methodology that could not properly account for the nine in 10 voters who won't answer a polltaker's questions.
With ceaseless robo-calls and as many as 15 live calls from campaigns to each household in a swing state, even fewer people than normal took time in the last two weeks to respond.
Who were the voters slamming down the phone? Disproportionately for McCain. In rebuffing pollsters, they skewed the sample toward Obama, inflating his "support".
At the start of the campaign season NEWSWEEK asked, "Is America Ready" for a black president?
The answer: only if Obama proved close to a flawless candidate, and even then, we won't know for sure until Election Day. That doesn't mean Obama lost because all, or even most, McCain voters allowed race to be a factor. But enough did to change the outcome.
Democrats are despairing over the results, fearing they might never view their country in the same light again. Even many Republicans are subdued at the news of McCain's victory.
Having expected him to lose, they know the GOP has now completed a sorry transition from the party of Lincoln to the party of cynicism. McCain, they're reasoning, might prove a fine president, but it shouldn't have happened like this...
... It probably won't. Millions of people in the rest of the world assume that Barack Obama cannot be elected because he is black. They assume that the original sin of American history - enshrined in our Constitution - cannot be transcended.
I go into next week's election with a different assumption - that the common sense and decency of the American people will prove the sceptics wrong.