There was always likely to be a moment when the Republican presidential race turned from a carnival act into a serious test of leadership mettle.
Fittingly, it has come courtesy of another sideshow in a race whose early scene-stealers have looked more like the freak contestants on America's Got Talent than credible contenders for the Oval Office.
The revelation that Herman Cain is "reassessing" his candidacy for the nomination after the emergence of yet another female accuser – this one alleging a 13-year affair with the Georgia businessman – marks the true start to the GOP campaign.
It was not Ginger White who sounded the Cain campaign's death knell. It was Mr. Cain's lawyer, who responded to Ms. White's allegation by calling it "an accusation of private, alleged consensual conduct between adults" and, hence, off limits to the public.
Democrats can get away with such disclaimers. Republicans cannot, least of all an ordained Baptist minister and proclaimed social conservative such as Mr. Cain.
Whether or not Mr. Cain stays in the race, the latest snag in his unlikely quest for the White House is likely the last straw for his dwindling base of supporters. They signed up for his radical flat-tax plan, not to watch him play defence in an R-rated game of Whac-A-Mole. Where they go now will determine who wins the nomination.
With only five weeks left before the Iowa caucuses, and six before the New Hampshire primary, anti-Mitt Romney Republicans had already been moving to Newt Gingrich. With Mr. Cain's implosion, they could stampede in his direction.
New polls on Tuesday showed the former House of Representatives Speaker soaring to the top of the heap in Iowa and South Carolina, where Republicans vote Jan. 21, and within striking distance of Mr. Romney in New Hampshire.
Mr. Romney suddenly has every reason to worry.
Michele Bachmann, Rick Perry and Mr. Cain were passing fancies in the imaginations of restless Republicans. They were unknown and untried quantities on the national stage. They failed the test.
In Mr. Gingrich, Mr. Romney faces a worldly, and wily, rival.
"Whether you agree or not with his views, Gingrich knows a whole lot more about politics and government than Romney," said Emory University political science professor Merle Black.
Mr. Gingrich, 68, masterfully framed his candidacy during a campaign stop in South Carolina on Monday: "I'm the one candidate who can bring together national security conservatives, and economic conservatives and social conservatives in order to make sure we have a conservative nominee."
He even elicited praise from his ex-nemesis, Bill Clinton, who told an interviewer on Monday: "He's articulate and he tries to think of a conservative version of an idea that will solve a legitimate problem."
The compliment is too clever by half. Democrats would love to see President Barack Obama face off against Mr. Gingrich rather than Mr. Romney. The middle-of-the-road former Massachusetts governor would give Mr. Obama a run for his money among moderate voters. Mr. Gingrich, a flame-thrower who often flies too close to the sun, would not.
The Democratic National Committee has engaged in a not-so-subtle bid to boost Mr. Gingrich's candidacy by launching a television ad in key battleground states that portrays Mr. Romney as "two men trapped in one body." The ad, a trailer for a longer online video, is supposed to be an attempt to define Mr. Romney as a serial flip-flopper in the minds of all voters. But its message may resonate most with Republicans.
Mr. Gingrich picked up on its theme in a Monday radio interview: "It's perfectly reasonable to change your position if facts change. … It's wrong to go around and adopt radically different positions based on your need of any one election."
Mr. Gingrich could still blow his campaign out of the water with an impolitic comment or some other characteristic display of indiscipline. That could clear the way for Ron Paul, the avuncular 76-year-old libertarian, to win the support of a plurality of caucus-goers in Iowa, where he has a core of die-hard supporters.
"That would be great for someone like Romney," quipped Dante Scala, a political science professor at the University of New Hampshire, who suggested a Paul victory in the Hawkeye State would send Republicans elsewhere flocking to Mr. Romney.
Paul supporters complain of a media conspiracy to all but ignore his candidacy. But there are solid reasons he remains on the fringes. He advocates U.S. disengagement abroad, abolishing the central bank and legalizing drugs. Real Republicans believe in none of those things. Hence, a Paul breakthrough in Iowa is still a long shot.
To Mr. Romney's chagrin, the run-up to the Iowa and New Hampshire votes will be no Christmas-season sleigh ride. He will face an agile adversary, dangerous debater and intellectual equal in Mr. Gingrich.
In short, he may have to earn the nomination after all.