By Catalina Camia and Jackie Kucinich

USA TODAY

Updated 2:48 p.m. ET

Herman Cain said today he is suspending his presidential campaign, acknowledging the toll it has taken on him and his family as he battled allegations of an affair and sexual misconduct.

The businessman vowed to endorse one of his GOP rivals and announced he would try to change Washington from the outside. Cain unveiled a new website, thecainsolutions.com.

"The pundits would like for me to shut up, drop out and go away," Cain said at a rally in Atlanta. "Well, as my grandmother who lived to be 104 years old used to say when somebody was dead wrong, 'Bless their little hearts.' "

The effective end of Cain's campaign is the latest twist in the volatile race for the GOP nomination. Six different people -- including Cain, a former CEO of Godfather's Pizza -- have been atop the USA TODAY/Gallup Poll.

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The current front-runner is former House speaker Newt Gingrich, whose own candidacy was on life support this spring. Gingrich and Cain are close friends, and Cain once said at a Republican debate that he'd pick Gingrich as his running mate if he had to choose from people onstage.

The leadoff Iowa caucuses will be Jan. 3 -- one month away.

Cain met with his wife, Gloria, and family Friday to discuss the allegations by Ginger White, an Atlanta woman who says she and Cain have had an off-and-on "sexual affair" for years. He said he gave White money to pay her rent and other bills without his wife's knowledge. Cain denied the affair and said he and White were only friends.

For Cain – the only major Republican candidate who has never held elected office -- the ride at times has been improbable. The longtime businessman, former trade group lobbyist and executive, and onetime radio talk show host was making only his second run for political office.

Cain billed himself as the unconventional candidate with the unconventional campaign, and rose from obscurity to upset the GOP field in September with a victory at the Florida straw poll.

From there, Cain started to receive national attention – and increased scrutiny – for his signature proposal calling for a 9% income tax, 9% corporate tax and new national sales tax.

By mid-October, he supplanted Texas Gov. Rick Perry atop the public opinion polls and was, for a time, the latest conservative alternative to Mitt Romney.

Cain hit a major roadblock Oct. 30, when Politico published a report about two women who filed sexual harassment complaints against Cain when he led the National Restaurant Association in the late 1990s.

Both women received cash settlements from the trade group. Cain strongly denied the claims.

Then Sharon Bialek, a Chicago-area woman, came forward and claimed Cain put his hand up her skirt and groped her as she sought his help finding a job in 1997. He said it "simply did not happen."

Bialek became the first woman to put a face behind the accusations, sparking an extraordinary news conference and round of interviews by Cain. His message was the same in each: He never sexually harassed anyone, the claims were "baseless" and "they" (referring at times to both the news media and Democrats) were trying to take him down.

Cain's recent troubles took their toll. He dropped in national and state polls, including a new one in Iowa where he was once neck-and-neck at the top with Mitt Romney. Although the Cain campaign said his fundraising was strong in October, there are news reports that the situation may have changed in recent days.

Cain's supporters gathered in Atlanta today for what was billed as a celebration for his new campaign headquarters. There were supporters attesting to his candidacy, music and food, then Cain and his wife, Gloria, appeared onsite.

They emerged from his campaign bus and walked hand-in-hand to the stage. Occasionally, the crowd chanted "Glor-i-a" and "Her-man."

Cain spent a few minutes thanking the crowd for getting him to what he called "the Final Four" of the presidential race. He told the audience it should take pride in proving "you don't have to have a political pedigree to run for president."

Then he acknowledged the price he and his family have paid.

"These false and unproved allegations continue ... to create a cloud of doubt over me and this campaign and my family," Cain said. "That spin hurts. It hurts my wife, it hurts my family, it hurts me and it hurts the American people because you're being denied solutions to our problems."

Cain is only the second major Republican to abandon his presidential bid. Former Minnesota governor Tim Pawlenty dropped out of the race in August after a poor showing in the Iowa straw poll.

Under the law, Cain can tap into the funds he has raised for the campaign as long as he doesn't use the money for personal reasons. He would be able to donate his presidential money to other candidates, party committees and charities. Cain could also return the funds or fold them into another political committee, such as a "super PAC."

(Contributing: Fredreka Schouten)