Acknowledging the "firestorm" arising from an accusation of infidelity, Cain only committed to keeping his campaign schedule for the next several days, in a conference call with his senior staff.
"If a decision is made, different than to plow ahead, you all will be the first to know," he said, according to a transcript of the call made by the National Review, which listened to the conversation.
It was the first time doubts about Cain's continued candidacy had surfaced from the candidate himself. As recently as Tuesday morning, a campaign spokesman had stated unequivocally that Cain would not quit.
Cain denied anew that he had an extramarital affair with a Georgia woman who went public a day earlier with allegations they had been intimate for 13 years.
"It was just a friendship relationship," he said on the call, according to the transcript. "That being said, obviously, this is a cause for reassessment."
He went on: "With this latest one, we have to do an assessment as to whether or not this is going to create too much of a cloud, in some people's minds, as to whether or not they would be able to support us going forth."
Saying the episode had taken an emotional toll on him and his family, Cain told the aides that people will have to decide whether they believe him or the accuser. "That's why we're going to give it time, to see what type of response we get from our supporters."
Ginger White's accusation of an affair prompted New Hampshire state Rep. William Panek, who endorsed Cain at a news conference earlier this year, to pull his endorsement and instead support former House Speaker Newt Gingrich in the upcoming primary. Panek said he rethought his position when White showed evidence that she traded 61 text messages and cell phone calls with the candidate.
"I felt like we were being lied to," Panek said. "I'm putting my name in New Hampshire as a state rep behind him and I just didn't like the way it was being played out."
In Iowa, Cain's campaign has lost some precinct-level supporters in light of the new allegations, Steve Grubbs, Cain's Iowa chairman, said during an interview with CNN.
Cain was in Iowa for a day last week to film a new ad, but spending to air it was on hold pending the fundraising in the days to come, Grubbs said.
"If people make contributions, then we'll keep the campaign doors open and be able to keep paying people," Grubbs said. "Otherwise, Herman Cain will have to make a decision whether he can afford to keep moving forward."
Cain has denied the affair as well as several other accusations of inappropriate sexual behavior that have dogged his candidacy over the past month. He had been publicly resolute about pressing ahead even as his standing in public opinion polls and his fundraising started to slide.
But in the conference call, he pledged only to keep his imminent schedule, including a foreign policy speech at Hillsdale College in Michigan later Tuesday that he promised to deliver with "vim, vigor and enthusiasm."
Speaking to nearly 1,000 people at Hillsdale, a conservative bastion, Cain didn't address the affair allegation. He stuck to his plan to present his foreign policy vision, one in which the U.S. would stand by friendly nations such as Israel, quit giving money to countries he considered enemies, and spend more on defense.
"Rather than the current philosophy of cut, cut, cut, I believe our philosophy should be invest, invest, invest," he said. "I happen to believe that we have allowed our military to get too weak."
While Cain avoided reporters after the speech, he would hardly be able to escape them at an event from which he withdrew earlier in the day: a party in New York on Sunday to meet with some of the city's top journalists including NBC's Matt Lauer and ABC's Barbara Walters. Cindy Adams, the New York Post columnist hosting the dinner, told the AP she had received a call Tuesday from Cain adviser John Coale saying Cain had decided not to attend. Coale declined to comment.
Still, Cain was what one participant described as calm and deliberate as he addressed his staff on the conference call.
The participant, Florida state Rep. Scott Plakon, one of four chairmen for Cain's Florida campaign, said he wanted to see more evidence from the accuser.
"If it is true that he didn't do this, I think he should fight and kick and scratch and win," Plakon said.
But if Cain did have the affair, Plakon said, it would be unacceptable to Republican voters.
"That would be very problematic," he said. "There's the affair itself and then there's the truthful factor. He's been so outspoken in these denials."
After the conference call, Cain attorney Linn Wood told the AP: "Any report that Mr. Cain has decided to withdraw his candidacy is inaccurate."
"I think they are assessing the situation, just as I would expect the campaign to do or any prudent business person to do," said Wood. He added that he would hate to see what he described as false accusations drive Cain out of the race for the presidency.
On Monday, Ginger White said in an interview with Fox 5 Atlanta that her affair with Cain ended not long before the former businessman from Georgia announced his candidacy for the White House.
"It was fun," said White, 46, as she described Cain buying her plane tickets for a rendezvous in Palm Springs, Calif. "It was something that took me away from my sort of humdrum life at the time. And it was exciting."
Cain went on television to flatly deny White's claims even before the report aired.
"I didn't do anything wrong," he said then. On Tuesday, he told his staff "I deny those charges, unequivocally," and went on to say he had only helped White financially "because she was out of work and destitute, desperate."
Seemingly out of step with Cain's denials, his lawyer issued a statement Monday that included no such denial of the affair and suggested that the media - and the public - had no business snooping into the details of consensual conduct between adults.
Cain's response was faster and more deliberate than he had managed when it was reported that three women alleged he had sexually harassed or groped them when he was the president of the National Restaurant Association in the mid- to late 1990s. The trade group paid settlements to two women who had worked there.
As some conservative Republicans sought an alternative to Mitt Romney, Cain surged in the polls while pushing his 9-9-9 tax plan and providing tough criticism of President Barack Obama during televised debates.
But as the harassment allegations surfaced, Cain stumbled in explaining his views about U.S. policy toward Libya and other foreign policy issues, creating an opening for rival Newt Gingrich to assert himself as a more reliable, seasoned politician to challenge Romney and even Obama. Cain fell in the polls and Gingrich began to rise.
In an email sent Tuesday to his supporters, Cain called the allegations of the affair "a fabricated, unsubstantiated story." He accused White of abusing their friendship.
"I am writing you today to assure you that this woman's story is completely false," Cain said in the email. "I do know Ms. White. I have helped her financially at times over the past few years, just as I have helped many friends and acquaintances throughout the years. I thought Ms. White was a friend in need of a supportive hand to better her life."
In her TV interview, White said she decided to come forward after seeing Cain attack his other accusers in an appearance on television.
Associated Press writers Kathy Barks Hoffman in Hillsdale, Mich., Beth Fouhy in New York, Thomas Beaumont in Des Moines, Iowa, Steve Peoples in Amherst, N.H., Greg Bluestein in Dunwoody, Ga., and researcher Barbara Sambriski in New York contributed to this report.