GREENVILLE, S.C. — Herman Cain slipped away from the tour group and into an office to talk with a worker. After hearing a 45-second synopsis of the woman’s duties at the computer software company, he clasped his hands and enthusiastically announced an “aha” moment.

“This is what people in Washington, D.C., don’t do enough of: get out and talk to real people solving real problems,” he said before moving on to another work station for another dose of real people wisdom.

While the backdrop was a quintessential campaign stop in this early primary state — he visited a complex housing small, start-up businesses to announce his tax cut-based economic vision — Cain is not a typical candidate.

Six months ago, the popular after-dinner speaker and Atlanta radio talk show host announced he was venturing into the national spotlight with a run for the presidency. The declaration mostly drew shrugs in political circles.

Now, with a little more than six months to go before the Iowa caucuses, Cain has managed to garner a third-place finish among Republicans, behind former Massachusetts Gov. Mitt Romney and Minnesota Rep. Michele Bachmann, in the Des Moines Register’s first poll. And that unexpected accomplishment has some of those same doubters paying a bit more attention.

More than 20 visits to Iowa in the past year have built Cain a passionate following, although “longshot candidate” still often precedes his name. Cain says he prefers the term “dark horse,” the black Republican’s eyes lighting up with mischievous glee at the political incorrectness.

It’s that kind of humor that has turned the former executive with an uproarious laugh and a plain-speaking, Southern style into a grass-roots sensation in the Republican field.

He recently signed a book deal and last weekend won a straw poll at a Cobb County GOP barbecue, getting more than triple the votes of his nearest rival, former House Speaker Newt Gingrich, who once represented that county. A Gallup poll released Friday found that 48 percent of Republicans and Republican-leaning independents know who Cain is, a 27 percentage-point jump in name recognition from late March. That’s the biggest improvement among Republican hopefuls.

Cain’s niche as the anti-candidate candidate (he has run for office just once, losing in the 2004 Georgia Republican primary for the U.S. Senate) has served him well in a year when being an outsider is cool.

“People are sick of politicians. They want someone fresh,” said Debbie Dooley of Gwinnett County, who was one of the founders of what became the national tea party movement. “People have a sense with Herman Cain that what you see is what you get.”

But with success comes scrutiny, from rivals and the media and, ultimately, the voters.

Recently, Cain found himself immersed in controversy after saying he would not be comfortable appointing a Muslim to his Cabinet or to a judgeship. And the political inexperience that gained him favor has also drawn criticism, especially in foreign affairs.

Most recently, several top staffers in both New Hampshire and Iowa quit. One, Charlie Gruschow, a founder of the Des Moines Tea Party, said he left because the campaign had gotten “just too messy,” though he didn’t eleborate.

Cain’s staff calls the defections “growing pains.” The campaign last week announced it had raised nearly $2.5 million in the most recent reporting period ending June 30. That’s on the low end among candidates, but Cain, who is 65, touts he has “no debt.” The reports have not been made public by the Federal Elections Commission, so it is unknown how much was his own money.

Some observers, like Steve Deace, a conservative activist in Iowa and a former talk show host himself, said Cain’s 15 minutes of political fame are waning.

“Herman Cain is the fastest growing supernova in the history of the Iowa caucuses,” Deace said Wednesday. “He burned bright and now is ready to go dark.”

Deace said Iowa’s Republican caucus is a relatively small circle of voters, with perhaps 125,000 coming out in 2012. He said word of Cain’s organizational woes and his “pat answers” to questions are spreading through those tight-knit conservative groups, causing people to turn to Bachmann or even Texas Gov. Rick Perry, who is thinking about running.

“The environment was there for (Cain),” said Deace. “There’s a lot of old, white conservatives who are tired of being called racists and who want to vote for a conservative black man. But he was unable to capitalize on it.”

Matt Towery, a former Republican legislator from Cobb and a political pollster, disagreed, saying Cain is doing pretty well.

“He has one big plus; he’s extremely charismatic and passionate,” said Towery. “I said he’d be a phenomenon in Iowa. They haven’t seen anything like him.”

Towery thinks Cain has staying power because he stands out from the other candidates.

During the South Carolina campaign stop, Cain huddled with his staff before conducting an interview with The Atlanta Journal-Constitution.

“My staff just scolded me in being too loose with the lips,” he said. “Because I’m showing up respectable in the polls, I’m going to get more coverage and more scrutiny.

“I’m still getting used to reporters looking for a faux pas and having to measure how you say certain things,” Cain said. He paused and laughed, “And I have failed that measure.”

Cain said he hadn’t come this far to settle for helping to set the Republican agenda.

“I honestly believe I can win,” he said, “which is my wife’s greatest fear. She has seen me achieve things against the odds for 43 years.”

During stump speeches, Cain likes to say he is the embodiment of the American dream: a black kid from Georgia who grew up in the segregated South, graduated from Morehouse College and Purdue University, where he got his master’s in computer science, then made it big in business. He worked for Coca-Cola and as a vice president at Pillsbury before heading Godfather’s Pizza and turning around the troubled restaurant chain.

His business acumen led him to head the National Restaurant Association. His ability to hold sway over large crowds brought him to inspirational speaking. His largest gig? “There were 14,000 in Cleveland, an Am-way convention,” he recalled. “They were hollering.”

Cain’s entry to politics came in 1994, when he confronted President Bill Clinton at a town meeting in Kansas City, Mo., as Clinton was selling his health care plan.

According to a Newsweek article from the time: “Cain asked the president what he was supposed to say to the workers he would have to lay off because of the cost of the ‘employer mandate.’ Clinton responded that there would be plenty of subsidies for small businessmen, but Cain persisted. ‘Quite honestly, your calculation is inaccurate,’ he told the president. ‘In the competitive marketplace it simply doesn’t work that way.’ ”

Many consider the exchange the beginning of the end for the plan.

It was another health plan, President Barack Obama’s, that energized Cain to consider a presidential run. Cain, who lives in Stockbridge, said he had overcome colon and liver cancer and was overjoyed at how American medicine moved quickly and aggressively to save his life. He said Obama’s plan would end all that.

He entered the race with some recognition from his restaurant association days, his speaking gigs and his radio show, which aired on AM 750 and 95.5 FM News/Talk WSB. But he needed to build up support.

“A year ago, I started talking to party officials and elected officials,” he said. “To be honest, most smiled politely. They just didn’t think I had a snowball’s chance in Hades.”

He said he had to wage a guerilla-style campaign.

“The traditional campaign model is you have immediate name ID, you have lots of money and you’ve held high-profile elected office. I didn’t have any of that! My game plan was first go for the grass roots, the tea party movement ... go for the regular folks.”

But a candidate still needs money to reach those to regular folks. A year ago, “we made an assessment of all the early support we can get. We had a lot of conversations with people who are wealthy, people who are professionals.”

A review of contributors to his Hermanator political action committee last year shows donations from top executives at companies like Hallmark Cards and Whirlpool, as well as from Robert McNair, owner of the Houston Texans. The list includes members of Americans for Prosperity, an advocacy group that funds tea party causes, and a $5,000 donation from a Georgian who was a big contributor to the 2004 “swift boat” campaign that attacked the Vietnam War record of Democratic presidential candidate John Kerry.

Many on the Hermanator list are Texans in the oil business, mostly because of Wayne Stoltenberg, a Dallas oil exec who heard Cain musing about a presidential run on his show.

“Whenever I can find someone who happens to be black but is a clear-thinking conservative, I send him money,” Stoltenberg said. He called Cain and left a message. Weeks later, a Cain aide called back. He asked Stoltenberg to donate $5,000 and get friends to kick in another $25,000 to $30,000. Stoltenberg did that and has become Cain’s guide when the candidate visits Texas.

The oil man likes Cain’s self-made-man narrative.

“We need a turnaround guy,” Stoltenberg said, “I’m from Texas, but George Bush is not that guy. We’ve had enough of trust fund babies. Herman Cain is not a trust fund baby.”

Cain said he has tried to remain close to his roots — all of them — straddling the line between his CEO friends and the “regular people” he so often touts in speeches.

Asked what his family members think about his politics, Cain laughs loudly.

“When we go to family reunions, we don’t talk politics” he said. “Many are lifelong Democrats, although now they aren’t diehard Democrats like they used to be.”

Cain said he has won some over.

He has got six months to do the same in Iowa.