Emotions run hot on election eve, and few emotions are more a-boil right now than liberal paranoia. I hear it constantly: I don't care about the polls. I won't believe it until I see it. The Republicans stole 2000 and 2004, and they'll steal this one.

This dark pessimism is fortified by a corollary anxiety that each new revelation about Barack Obama will surely bring the whole enterprise crashing down and make middle Americans wake up and say to themselves, "Of course. What was I thinking? Back to McCain!"

This past weekend it was the story about Obama's auntie in Boston, a woman living in the US illegally for the last four years. But Zeituni Onyango is fading into the background, just another element of the farrago of last-minute titbits that make for future trivia questions. Her name may have been unlawfully leaked to the press by officials seeking to do Obama damage. But whatever the truth of that matter, the injury to Obama would appear to be minimal.

And yet, some liberals feared that this revelation would be the death knell. But in their terror, they have probably not stopped to ask themselves: if Bill Ayers and Jeremiah Wright and Rashid Khalidi - the Palestinian rights advocate with whom Obama is friendly and whom McCain smeared last week - didn't blow up this campaign, why would Onyango?

Face it, liberal paranoiacs: the swift-boating of Barack Obama clearly is not working. That it would work - indeed that it would define the contest - was the greatest fear of liberals everywhere as it became clear last spring that this somewhat unusual creature would carry the Democratic standard into battle this autumn. Many foresaw an October full of racial innuendo, Obama-Osama Freudian slips and worse.

Sure enough, we did see a lot of it. John McCain and Sarah Palin worked overtime to try to persuade Americans that Obama shared Ayers's radical world view. McCain's disgraceful comparison of Khalidi to a "neo-Nazi" - this about an American citizen by birth who teaches at an Ivy League university and has no record of extremism beyond that which can be conjured on rightwing websites on the basis of the odd out of context quote - was perhaps the lowest point of his whole campaign. And the Republicans have used race in subtle ways - the argument that Obama would take people's hard-earned tax dollars and hand them to idlers on "welfare" is a very old racist trope in the US.

Here in the 11th hour, we are hearing that Obama is unpatriotic and a friend to criminals; that he's not really a citizen of the US (disproved over the weekend by birth registrars in the state of Hawaii); and that his election will lead to a second Holocaust.

Yes, the voting is still a day away. But so far none of it has amounted to a single point in the polls that I can see, except perhaps in some southern states where tradition dies hard. Why? Three reasons.

First, the Obama team has responded quickly whenever such allegations have arisen. John Kerry's advisers let a fateful 15 days of swift-boating pass before they even addressed the issue. Obama's people haven't made that mistake. They've answered all charges and usually turned around and levelled a few charges of their own.

Second, the economic crisis really has fixed many voters' minds on more germane questions. Voters are more susceptible to character attacks when times are good and they don't have real bread-and-butter issues to worry about. But when times are tough, they actually do listen a little harder to discern which candidate seems to be more serious about addressing their problems.

The third reason is historical and is just my theory, but I think it's right. Broadly speaking, the American electorate consists of three chunks: committed conservatives, committed liberals and the uncommitted swing voters in the middle. When Ronald Reagan realigned American politics in 1980, he did so by forging a strong emotional alliance between the right and the middle. Centrist voters gave Republicans and conservatives the benefit of the doubt and looked upon Democrats and liberals, whom Reagan successfully discredited, with deep suspicion.

In that context, charges that Democrats weren't good Americans tended to stick. Whether it was Michael Dukakis's membership in the American Civil Liberties Union in 1988 or Kerry and the swift-boaters last time around, conservative allegations that Democrats seem alien and elitist and not fully American took hold with voters in the middle. They accepted terms of argument set by the Republicans.

But post-George Bush we're in a new context. That coalition of affinity that Reagan created between right and middle, Bush has put asunder. His failures have made the average, apolitical American as distrustful of conservatism as he or she once was of liberalism - indeed somewhat more so, since the memory of conservative failure is fresher in the mind. This is a new context. Many experts have yet to grasp it. Certain elements within the mainstream media haven't quite got it yet. And clearly some liberals just can't believe that it might be the case.

This is not to say that negative campaigning will disappear as of tomorrow. But it is to observe that political contexts change, and eras end. I'm still suspicious enough to use the conditional tense, but by Wednesday morning even the most paranoid liberals may be forced to accept that fact.

• Michael Tomasky is the editor of Guardian America. Read his blog and watch his video commentary at theguardian.com/commentisfree/michaeltomasky