Wife's verdict awaits Cain as he admits 'friend' was a secret

Herman Cain's bizarre odyssey seemed near an end yesterday as the pizza magnate-turned-White House candidate headed home for discussions with his wife about a woman's claim she had a 13-year affair with him, his former front-runner status in the contest for the Republican nomination no more than a distant memory.

Mr Cain was making one last campaign stop in South Carolina, which holds one of the earliest primaries, before his first trip back to Atlanta and his family since Ginger White went public with her allegation of the affair, which in her version of events only ended a couple of months ago.

Thus far Mr Cain has only promised a decision by Monday on whether to remain in the race. He denies any romantic liaison with Ms White, a 46-year-old one-time fitness instructor, saying he merely gave her money to help her over financial difficulties.

"My wife understands that I'm a soft-hearted, giving person," he said in an interview with the New Hampshire Union Leader. But, he acknowledged, Gloria Cain did not know he was making the payments, for "month-to-month bills and expenses".

But the outlook for his campaign grows darker by the day. A new poll by The Des Moines Register, shows Mr Cain's support in Iowa has plunged to just 8 per cent. That compares with 31 per cent in late October, before the initial allegations that he sexually harassed four women, followed by several embarrassing foreign policy fumbles, and now Ms White's claim of an extra-marital relationship.

The candidate has admitted his fundraising is drying up, while social conservatives, vital in Republican primaries, are deserting in droves. Washington's professional pundits have long since written off his campaign.

As Mr Cain's fortunes have tumbled, so those of Newt Gingrich have risen. The former Speaker of the House is the latest and – given the proximity of the first voting – maybe the last candidate to emerge as an alternative to Mitt Romney, long the consensus front-runner, but who has failed to enthuse the Republican faithful.

Mr Gingrich may be precisely the sort of veteran political insider that rank-and-file Republicans are supposed to detest. But, thanks to a string of competent performances in the candidates' debates, he is the flavour of the moment. In the past week he has jumped into a double-digit lead in Iowa.

In the far bigger and more important state of Florida, which holds its primary on 31 January, he is currently 31 points ahead of Mr Romney, the candidate deemed by most polls to have the best chance of beating President Obama next November. Even in New Hampshire, where Mr Romney had seemed unassailable, Mr Gingrich has cut Mr Romney's lead to just 10 per cent.

But Mr Gingrich's staying power, though surely greater than Mr Cain's, is questionable. Three-times married, the former Speaker carries much personal baggage. His consulting activities, collectively described by critics as "Newt Inc", have long attracted controversy.

Above all he has a self-destructive streak. Lack of self-esteem has never been a Gingrich deficiency, and that trademark self-confidence, verging on cockiness, was on display in an interview yesterday with ABC News. "It's very hard not to look at the recent polls and think that the odds are very high I'm going to be the nominee," he said.

Mr Cain's misadventures, however, are a lesson that, in this unpredictable Republican race, anything can happen.