ROCK HILL, S.C. (AP) — His once-surging presidential campaign all but over, Herman Cain told supporters Friday he would make an announcement Saturday about the future of his Republican White House bid.

Cain, who was heading home Atlanta to talk with his wife, didn’t disclose whether he would drop out of the race for the GOP nomination after this week’s allegation that he had a 13-year extramarital affair. He told supporters simply to stay tuned.

“Nobody’s going to make me make that prematurely,” Cain said. “That’s all there is to it.”

In his remarks in South Carolina, he sent a mixed message as to his intentions. He said he would clarify the next steps of the campaign and assured supporters the affair claim was “garbage.” But he also said he needed to consider what he would do with campaign donations already banked if he dropped out of the race.

It’s hard to see how he goes forward. His poll numbers have dropped dramatically, backers are fleeing and even the candidate himself has acknowledged that fundraising has suffered since Ginger White publicly contended the two had had a long-running affair.

A Des Moines Register poll released Friday showed Cain’s support plummeting, with backing from 8 percent of Republican caucusgoers in Iowa, down from 23 percent a month ago.

The embattled candidate was meeting with his wife face to face for the first time since White stepped forward this week.

Cain has denied the allegation, even as he has acknowledged what he called a friendship with the woman that included payments for what he said was financial hardship, “month-to-month bills and expenses.” He has said his wife didn’t know of his connection to White.

“My wife and family comes first. I’ve got to take that into consideration,” Cain told a crowd of about 100 people in South Carolina. “I don’t doubt the support that I have. Just look at the people who are here.”

He urged his backers to look past the allegations. In addition to the most recent one, he has been accused by several women of harassing them when he was president of the National Restaurant Association.

“There’s a lot of garbage on the Internet. There’s a lot of garbage out there on the TV. There’s a lot of garbage out there about me, don’t you know? There’s a lot of misinformation out there. You have to stay informed and check out the facts for yourself,” Cain said.

He added: “I’m on this journey for a reason. I don’t look back.”

Word of a pending announcement took some aides by surprise.

“I am learning this as you’re learning it,” said Cain’s Iowa campaign chairman, Steve Grubbs, who met Thursday in Iowa with campaign manager Mark Block.

The two outlined a December travel schedule for Cain, who began advertising on television again in Iowa on Friday.

As of that afternoon, Cain was scheduled to participate in the two Iowa debates this month, hold a media announcement in Iowa on Dec. 12 and tour the state at the end of the month.

“That’s sort of the plan, very tentatively,” Grubbs said. “All that could change.”

Georgia supporters set to attend the Saturday event in Atlanta — to celebrate the opening of a national headquarters — were taken aback by the news that an announcement was coming.

“I have heard nothing,” said state Sen. Josh McKoon, a prominent Cain backer who will stand with him Saturday.

With a little more than a month before Iowa has its lead-off caucuses, time is working against the Georgia businessman.

On Thursday night, White told MSNBC in an interview that she was “deeply sorry” for causing Cain’s wife or other members of his family any pain.

“My heart bleeds for this woman because I am a woman and being in a situation like this cannot be fun. And I am deeply, deeply sorry if I have caused any hurt to her and to his kids, to his family,” she said.

White said the affair was never about love and that Cain never said he loved her.

“Nor did I tell him that I loved him,” she said. “It wasn’t a love affair. It was a sexual affair, as hard as that is for me to say and as hard as it is for people to hear it. You know, it pretty much is what it is. And that’s what it was.”

Even before White surfaced, Cain faced steep hurdles to the nomination. He didn’t have much of a campaign organization. He was spending more time on a book tour than in early primary and caucus states. And he was dealing with doubts about whether he was ready for the presidency, given a series of fumbles on policy questions.

He canceled a Friday evening event at the Atlanta Athletic Club.

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Associated Press writers Shannon McCaffrey and Ray Henry in Atlanta and Tom Beaumont in Iowa contributed to this report.

Copyright 2011 The Associated Press.