ATLANTA — The brief but dramatic campaign of Herman Cain ended on Saturday, when the little-known businessman who captivated the Republican race said the relentless attention on accusations of his sexual misconduct had become too much to bear.

Both defiant and passionate, Cain again denied allegations of sexual harassment and an extramarital affair, while declaring, “I’m not going away.”

But, he said, after “a lot of prayer and soul-searching I am suspending my presidential campaign because of the continued distraction, the continued hurt caused on me and my family.” Cain also cited difficulty in raising enough money to remain competitive.

Cain’s decision is the latest twist in a Republican primary contest that has been marked by a search for a conservative alternative to Mitt Romney, the establishment favorite.

After a string of impressive debate performances, Cain assumed that role in late September. But amid mounting allegations and a series of gaffes, much of his support has shifted in recent weeks to former House Speaker Newt Gingrich, who has joined Romney atop the polls.

Cain gave no indication on Saturday who was his second choice for president, but he said he will endorse one of his former rivals “in the near future.”

In a Republican nominating contest that has see-sawed from one front-runner to another, Cain, 65, was perhaps the unlikeliest to rise to the top of the pack. A former pizza executive with no political experience, little campaign organization and a schedule tailored more to selling books than winning votes, Cain nevertheless captured the hearts of Republican voters with a clear message, confidently delivered.

“I’m upset. I feel like the other side won, their dirty tricks,” said Marelli Gardner, a health-care coordinator and tea party activist from Cummings, Ga., who drove 45 minutes and waited two hours to hear Cain speak on Saturday. She left before his remarks were over. “A lot of people had a lot of hope in Herman Cain.”

At his rally Saturday, Cain said, “I have made many mistakes in life, everybody has.” But he also offered his story as evidence of the nation’s strengths.

“I grew up in a world of segregated water fountains,” he said. “My father was a chauffeur and my mother was a maid. We showed that you didn’t have to have a degree from Harvard in order to run for president. We showed that you didn’t have to have a political pedigree. . . . I am proof that a common man could lead this nation.”

In a field of politicians and Washington insiders, Cain presented himself as the businessman outsider with “bold new ideas.” While Romney had a 59-point economic plan and a 160-page book to explain it, Cain said the nation’s ills could be fixed with three simple numbers: 9, 9 and 9.

Cain talked so incessantly about his “9-9-9” tax plan, which would have scrapped the current tax code and replaced it with a 9 percent tax on individuals, a 9 percent tax on businesses and a 9 percent sales tax, that it became both a punch line and a selling point.

On the campaign trail, Cain attracted large crowds who were drawn to his straightforward style, folksy sayings (“Awwww shucky ducky now!”) and affability. More than once, he delighted crowds by breaking into song. Released in the midst of his presidential run, his latest book, “This Is Herman Cain!”, became a bestseller.

Cain also embraced his role as the first African American to rise to the top tier of a Republican nominating contest. When asked whether he was the flavor of the week for Republican voters, Cain told Jay Leno to call him “Haagen-Dazs Black Walnut” because “it tastes good all the time.” And he used his up-by-my-bootstraps story of growing up poor and black in Atlanta to connect with voters and extol American values.

But for the past month, Cain has held on as an embattled candidate, denying accusations that he had sexually harassed several women when he headed the National Restaurant Association in the 1990s.

On Monday, Atlanta businesswoman Ginger White alleged that she and Cain had carried on a 13-year affair. Cain acknowledged a friendship with White and said he had been helping her financially, but insisted it was not sexual.

The former Godfather’s Pizza chief executive has fiercely denied all of the accusations, and said to his supporters on Saturday that “one of the first declarations I want to make with you today is that I am at peace with my God. I am at peace with my wife. And she is at peace with me.”

Cain’s small campaign staff proved unable to effectively respond to the allegations, with Cain often contradicting himself or his advisers.

Scott Plakon, a Florida state legislator and co-chair of Cain’s campaign in the state, said he had never seen a campaign so full of ups and downs. For the past month, he watched the downward slide.

“It got beyond them,” Plakon said of Cain’s small staff. “He had to run one type of campaign when he was at 5 percent in the polls, but when you start getting attacked there is another skill set that’s needed and they just didn’t have that.”

Cain didn’t help his cause by making a series of gaffes that showed his limited grasp of many issues, particularly foreign policy.

Cain’s announcement that he is suspending, rather than terminating, his campaign appears to give him greater flexibility in the months ahead to transfer leftover funds to a candidate or political committee of his choice. “Suspension” has no legal meaning under Federal Election Commission rules, meaning Cain could continue to raise contributions and spend money until declaring a formal end to the campaign.

Plan B, as Cain put it, will be an organization that will allow him to “continue to be a voice for the people” and promote his tax plan. As of Saturday, it consisted of a single Web page, TheCainSolutions.com, where supporters could submit their email addresses and await more information.

Cain had said earlier in the week he planned to stay in the race, but he was aware that the allegations were hurting his family. He traveled to Atlanta Friday for his first face-to-face meeting with his wife, Gloria, since White alleged the affair.

Cain and his wife gathered with about 10 of his most ardent supporters Saturday morning to relay his decision. Gloria Cain sat quietly, listening intently to her husband as he said suspending the campaign would “liberate” him and stop the news media from airing the accusations against him.

“Contrary to what the scandalous, nameless, faceless character assassins intended to do, Mr. Cain is not going away anytime soon,” said Niger Innis, a campaign adviser who was in the smaller meeting. “I think he did not want to leave the race. He came to the conclusion that he just could not put his family through the attacks.”

Somashekhar reported from Atlanta and Thompson reported from Washington. Staff writers Chris Cillizza and Dan Eggen also contributed from Washington to this report.