As support plummets in Iowa and elsewhere, Cain to decide whether to stay in race after face-to-face talk with his wife Gloria

Embattled Republican candidate Herman Cain promised to announce Saturday afternoon at an event in Atlanta, Georgia, whether he will quit the race after a week in which he faced fresh sex allegations, saw donations begin to dry up and his poll ratings go into free fall.

Speaking at a campaign event in Rock Hill, South Carolina, Friday, he offered no hint of his decision, whether to battle on in the hope of recovering lost support or pull out.

"I am reassessing because of all this media firestorm stuff," he told the audience, adding that his wife Gloria and his children came first. He was due to meet Gloria at their home outside Atlanta late on Friday for their first face-to-face meeting since Atlanta businesswoman Ginger White claimed on Monday she had had a 13-year affair with him.

Cain told the audience he did not doubt that he retained a strong level of support among Republican voters. "Tomorrow in Atlanta, I will be making an announcement," he said.

His statement caught some of his staff off-guard. His campaign organiser in Iowa, Steve Grubbs, only moments before Cain's speech, denied there would be a major announcement Saturday.

Cain has demonstrated he is more tenacious than most candidates, carrying on in spite of a spate of negative reports that would have sunk other campaigns. He has survived four women coming forward to accuse him of sexual harassment. On top of this, his lack of knowledge of foreign affairs has been cruelly exposed in recorded interviews.

He said on Thursday night he would make a decision on whether to remain or stay by Monday.

Support for Cain has gone into a nosedive in Iowa, one of the key early states, according to a poll in the Des Moines Register.

The poll, published Friday, shows support among likely Republican caucus-goers has dropped from 23% in October to 8%. The first of a series of allegations that he had sexually harassed women emerged on October 31, but he appears to have suffered the most damage from a claim by White of a long-lasting affair.

The polls over the last few months have been volatile, and even now only an estimated third of potential caucus-goers have made up their mind who they will support. But the Des Moines Register poll has a good track record, being one of the few that was relatively accurate during the 2007-8 campaign.

Ed Rollins, who was campaign manager for the Republican candidate Mike Huckabee who won Iowa in 2008, told Fox News Friday that he thought Cain's campaign was effectively over and predicted he will quit the race over the next few days. "He is dropping like a rock," Rollins said. Cain could either get out or stay in and be clobbered, he added.

The Des Moines Register poll, carried out between November 27 and 30, was of 401 likely Republican caucus-goers. Iowa holds the first of the Republican nominating contests on January 3.

One of the most telling details in the poll is a sudden drop after Ginger White claimed in a television interview broadcast on Monday evening that she had had an affair with Cain. He denies it, acknowledging her as a friend he had helped out financially on a regular basis but insisting they had no sexual relationship.

On Sunday and Monday, 22% of those polled said he was the candidate they would most like to meet in person. Those polled on Tuesday and Wednesday showed a fall to 8%. Overall support for Cain stood at 12% on Sunday but had dipped to 4% by Wednesday.

Grubbs, Cain's campaign manager in Iowa, admitted that support for Cain in Iowa had slowed this week and the Des Moines Register's poll was not good news. But he told the Register that only 2% of the precinct captains needed to organise the caucus had deserted.

He said they had 901 precinct captains in place out of the 1,700 needed to get out the vote on January 3.