"Over the last couple of weeks, I've been through hell," Cain said at a stop in Kalamazoo.
"But here's the good news: It didn't kill me or slow me down one bit," he told the crowd of more than 400 who packed a hall to hear him speak.
Supporters seemed undeterred by the furor surrounding Cain, and he kept to friendly territory: tea party groups that make up the core of his support. He's trying to keep ignited the grassroots spark that shot him to the top of the GOP field before the allegations of sexual harassment became public. He has denied behaving inappropriately.
"How you beat Obama? Beat him with a Cain!" the Georgia businessman told one supporter as he pushed through the crowd toward a back exit at the Blue Sky Diner in Ypsilanti, near Detroit. The crowd cheered Cain's comments.
When a reporter asked him to clarify what he meant, Cain said: "Cain. Herman Cain, C-A-I-N. Do I have to connect all the dots for you?"
"I don't believe any of the bull. I think it's just a slam," Kathy McConnell, a retired truck driver from Sumter, said of the allegations that have besieged Cain's campaign the past two weeks.
The crowd - and Cain's security detail - jockeyed with photographers and reporters pressed into the small diner. At one point, Cain's security guard reached out and pushed a reporter who was trying to listen to the candidate.
Cain also stopped in Battle Creek and Grand Rapids and planned an evening event in Traverse City, in northern Michigan.
One of Cain's Republican opponents and fellow Georgian, Newt Gingrich, took a not-so-subtle swipe at Cain's woes in a Web ad released by his new political action committee. The spot fixes a picture of Cain next to footage of Republican Michele Bachmann who says, "We can't have any surprises with our candidate." As she speaks the image of Cain shatters. Gingrich had at one point condemned media coverage of the Cain allegations.
Far from backing down in the face of his challenges, Cain has hired a fierce new lawyer to help him fight the four women's claims "in the court of public opinion." And he's pushing forward with a more aggressive campaign strategy to get his message out, airing his first television ad in Iowa and preparing to sign a lease on a cavernous new campaign office in Atlanta that will serve as a hub for volunteers.
Late Thursday, the attorney for one of the women, Karen Kraushaar, said plans for a joint news conference with all of Cain's accusers had been shelved. Joel Bennett said Kraushaar had received no response from two of the four women who allege that Cain sexually harassed them more than a decade ago, when he headed the National Restaurant Association.
The fourth woman, Sharon Bialek, had agreed to join Kraushaar at the news conference.
Still, there are signs that the accusations could be causing Cain's luster to dim. Uneasiness is growing among Republicans less than two months before voting begins in Iowa.
Private polling shared with The Associated Press shows Cain's support in Iowa has declined since last month. Internal polls of likely Republican caucusgoers showed Cain's support consistent with The Des Moines Register's poll in late October, which showed him narrowly leading in the state with 23 percent. The private polls showed Cain still in double digits in Iowa, but markedly lower.
The scandal also was filtering down to the grass roots in Iowa, where Cain volunteers were proceeding with nightly calls to potential supporters armed with a response to questions about the allegations. Volunteers were told to echo Cain's denial of wrongdoing.
"When we are trying to convince someone to be a team leader, we answer their questions," said Steve Grubbs, Cain's Iowa campaign chairman. "The answer to that is: Tell them what Herman Cain is saying."
The Cain camp seemed to be making efforts to shore up support among women, including by rolling out the endorsement of a prominent Republican female state lawmaker in his home state of Georgia, Renee Unterman.
Cain's new lawyer, Lin Wood, could provide polish and focus to a candidate who struggled to stick to a consistent version of events as the story broke.
In an interview with The Associated Press, the Atlanta-based lawyer whose high-profile roster of clients has included the family of Jon Benet Ramsey and wrongly accused Olympic park bomber Richard Jewell, said he would help the campaign "evaluate and respond to" the women's claims.
"Mr. Cain is being tried in the court of public opinion based on accusations that are improbable and vague," Wood told The AP. "The media - bless your heart - you turn our system of justice into one of guilt by accusation."
But Republicans worry privately about Cain's impact on a nominating contest that's about to start in earnest. While no one is rushing to push him out of the race and he has vowed to remain a candidate, the chorus is growing for the former pizza company executive to explain the allegations of unwanted sexual advances that have come to light more than a decade after they are said to have happened.
"It's one of the he-said-she-said stories," said GOP strategist Greg Mueller. "But you want to put the story to rest as quickly as you can and let the voters decide. It seems like every day it's a new elevation of the story. Either that's going to peter out or it's going to solidify."
Four women have said Cain sexually harassed them in the 1990s when he headed the National Restaurant Association. Two have come forward publicly, including one who had filed a sex harassment claim and reached a settlement with the group.
Associated Press writers Philip Elliott in Washington and Thomas Beaumont in Des Moines, Iowa, contributed to this report. McCaffrey reported from Atlanta.