For sheer craziness, few events on the American political calendar beat the annual gathering in a cavernous Washington hotel each February of the Conservative Political Action Conference.

Republicans with the slightest instinct for compromise need not apply. A CPAC is part political trade fair, part motivational course for tomorrow's right-wing true believers, and not least an opportunity for the further fringes of the party to vent their innermost prejudices.

And in the past these conferences have featured some strange stars. In 1994, CPAC was where Paula Jones first went public with her allegations of sexual harassment against then President Bill Clinton. But the CPAC that wrapped up here last night was different. For once, it may have really mattered.

For that, thank the calendar of this extraordinary Republican presidential race. This time last week, Mitt Romney, fresh from convincing wins in Florida and Nevada, looked to have the nomination in the bag. Then came Rick Santorum's sweep in Missouri, Colorado and Minnesota – meaning that the frontrunner had actually lost five of the first eight primaries and caucuses, four of them to Santorum and one to Newt Gingrich. And so to CPAC, at which all three made their pitches.

In truth, the Santorum hat-trick was less than met the eye. In Colorado and Minnesota, turnouts were derisory. In the latter's caucuses fewer than 49,000 took part – equivalent to 4 per cent of the votes cast in the state for Republican candidate John McCain in November 2008. Those who did take part were not the committed, but the ultra-committed. That vote proved not so much the popularity of Santorum (although he is a nice enough fellow) but the continuing refusal of the base to embrace Romney.

Now the latter is still favourite, at least as long as Messrs Santorum and Gingrich continue to split the conservative vote. In Missouri, the former House speaker was not on the ballot and Santorum won an outright majority of 55 per cent. There's no sign of it happening, but if either was to drop out, then Romney would be in dire trouble.

Even so, rarely has a frontrunner been less convincing. Romney's problem is that of the boss of the dog food company of legend, bewildered why his product won't sell despite having the best ingredients and an unmatched marketing operation. A minion finally pipes up: "But dogs don't like it."

For dogs, read the evangelical and social activists who remain suspicious of a candidate branded by his successful governorship of liberal and sinful Massachusetts. To them, Romney seems a fraud, all things to all men, without a political fibre in his body beyond an inflexible desire to win the White House. Perhaps these unhappy beasts will know what's best for them, and dutifully swallow the dog food. But perhaps not. CPAC was a chance for Romney to win over true conservatives, live on television.

He did his best. He declared himself not just conservative, but "severely conservative". He vowed to repeal Barack Obama's healthcare reform. He proclaimed the dawn of a new conservative era. He touted his record of having never served a day in Washington, the fount of government and therefore of all evil. But for all the hollering of the Romney faithful in the hall, you couldn't be sure.

An hour earlier Santorum had been introduced by his key financial backer, the investor Foster Friess. "A conservative, a liberal and a moderate walked into a bar," Friess joked. "The bartender said, 'Hi Mitt!'" Santorum is a mint-certified social conservative, to whom abortion and gay marriage are anathema. Whatever he lacks, it isn't authenticity. He spoke for barely 15 minutes. But the welcoming ovation he received sounded more sincere.

Santorum questioned his opponent's supposedly greater electability, one of the main selling points of Romney-brand dog food. "Why," he asked, "would an undecided voter vote for a candidate the party's not excited about?" And, he urged: "Walk out of this gathering and choose the person who makes you say, 'I have done my duty, I have kept my honour.'"

Did Romney persuade the doubters? One indicator was yesterday's Maine caucuses. Romney only just beat – by 39 per cent to 36 per cent – Ron Paul, his only rival to campaign here. Earlier, he edged Santorum in a CPAC straw poll by 38 per cent to 31. Far more important will be the primaries in Arizona and Michigan at the end of February. A defeat in his birth state of Michigan would be devastating, but cannot be ruled out. And if the frontrunner were to lose there, the desperation in the Republican establishment truly would be something to behold.