It wouldn’t be the first primary race in Wisconsin to spring a surprise. Forty years ago, Hubert Humphrey headed into an Easter-week Democratic primary with a healthy lead in the opinion polls, only for George McGovern to score an upset victory that established him as the front-runner.

“The results were such a jolt to the Conventional Wisdom,” Hunter S. Thompson wrote, “that now—with a cold gray dawn bloating out of Lake Michigan and Hubert Humphrey still howling in his sleep despite the sedatives in his room directly above us—there is nobody in Milwaukee this morning, including me, who can even pretend to explain what really went down last night.”

If Rick Santorum somehow defies the polls tomorrow night and comes out ahead of Mitt Romney, the Good Doctor might well rise from his grave to record the moment. My, how he would have enjoyed this campaign—at least, before the booze, the drugs and the writer’s block sent him nuts with self-loathing. An asset-stripping Mormon gazillionaire versus a Roman Catholic home-schooler who makes Pope Benedict look like a subversive liberal. Still lurking in the background: a puffed-up Georgian squarehead who conducts himself like a latter-day Herodotus and a fiery Texan goblin who wants to abolish the Federal Reserve. Gone but not forgotten: Rick “Oops” Perry, and Herman”9-9-9” Cain.

What fun we’ve had over the past eight months. Now, though, the killjoys at Republican HQ are intent on unplugging the sound system and telling the revellers that its time to go home. Having deliberately devised this extended primary season as a means of focussing attention on the party, the G.O.P. geniuses have decided it has been rather too successful, and it’s time to round upon President Obama. Hence the raft of endorsements Romney has received in recent days, including two timely shout-outs from Wisconsin’s best-known Republican politicians: Congressman Paul Ryan and Senator Ron Johnson.

Thankfully, Santorum hasn’t got the message. On the eve of the voting, he’s still out there in the cities and small towns of Wisconsin, making stops at bowling lanes, building-supply stores, and cheese factories. This afternoon, he is due to speak in Ripon, population 7,680, the unofficial birthplace of the G.O.P. (In 1854, a small group opposed to the pro-slavery Kansas-Nebraska Act met there and took on the name “Republicans.”) All in all, Santorum has visited twenty-five of Wisconsin’s counties. Romney has visited just five. (He’s adding another five today.)

Will history and shoe leather carry Santo to victory? Probably not. A month ago, a survey from the polling firm P.P.P. showed him sixteen points ahead of Romney. In a new poll that P.P.P. released today, Romney is up by seven points: forty-three per cent to thirty-six per cent. Other polls present a similar picture. Of six that were taken over the past week, not a single one showed Santorum ahead. Romney is feeling so confident that over the weekend he publicly predicted a victory.

There’s no mystery about what has turned things around for the Mittster. The recent endorsements were helpful, but what really moved the polling numbers was negative campaigning and money. In the past few weeks, Romney and his Super PAC have outspent Santorum by four to one, blanketing the local airwaves with negative ads. Santorum has responded with some shots at Romney’s record, including a rather clever spot that compares it to Obama’s. But that ad is only going statewide in Wisconsin today—a fact that says pretty much everything about Santorum’s campaign, and how ill organized it is compared to the Romney machine.

Still, until I see some actual voting returns from the suburbs around Milwaukee and Green Bay, I wouldn’t entirely rule out another Santorum shocker. He’s outperformed his poll ratings in other states, and it would be no surprise to see him do it again. But for him to win rather than come close, he needs a last-minute swing in his favor. Actually, in the new P.P.P. survey, there is a hint of one. Among voters who have decided in the past few days, Santorum is leading Romney by fifty-two per cent to twenty-seven per cent. (Unfortunately for Santorum, these people only made up nine per cent of respondents.)

Betting on Romney in a heartland state like Wisconsin is always a risky proposition. Santorum won the neighboring states of Iowa and Minnesota. Again tomorrow, he will have some things going in his favor. About forty per cent of the electorate will be drawn from rural areas, where Romney always does badly. If Santorum can rack up big victories in the sparsely-populated outlying regions, the race will come down to the suburban counties in the southeast of the state—such as Waukesha, Washington and Ozaukee, which are all near Milwaukee.

The voters in these counties are almost all white: about half of them are of German extraction. But as Craig Gilbert, a columnist at the Milwaukee Journal, pointed out yesterday in an insightful piece, they are “less moderate, less affluent, and more socially conservative than the white-collar suburbs Romney won so easily in Illinois two weeks ago.” Santorum has been a frequent visitor to this area, and, as evidenced by his mean bowling form, he is a much better cultural fit there than his strike-challenged opponent.

A victory for Romney tomorrow would see a concerted effort on the part of the G.O.P. establishment and the media to proclaim him the nominee-elect. A defeat would extend his torture. With a win in Maryland, where he’s heavily favored, he’d probably end the day winning more delegates than Santorum anyway. But Tampa would still seem a long way off.

Photograph by Eric Thayer/The New York Times/Redux.