Former pizza chain manager Herman Cain, a favourite of the ultraconservative tea party movement, has joined the race to be US president despite never having held elective office.
"I'm running for president of the United States, and I'm not running for second," he told a crowd at Atlanta's Centennial Olympic Park.
Chants of "Herman" erupted from the crowd of thousands.
The announcement by the black businessman, author and talk radio show host that he was joining the expanding Republican field came after months of travelling around the country to introduce himself to voters.
Now the 65-year-old will see if he can use that grass-roots enthusiasm to turn a long-shot campaign into a credible bid.
Mr Cain supports a strong national defence, opposes abortion, backs replacing the federal income tax with a national sales tax and favours a return to the gold standard.
He said President Barack Obama "threw Israel under the bus" because he sought to base Mideast border talks partly on the pre-1967 war lines, and criticised the Justice Department for challenging Arizona's tough crackdown on illegal immigration.
"We shouldn't be suing Arizona," he said to cheers. "We ought to send them a prize."
Mr Cain lost a three-way Republican US Senate primary bid in Georgia in 2004 with one-quarter of the vote.
His "Hermanator" political action committee has taken in just over 16,000 US dollars this year. Supporters say he taps into the tea party-fuelled desire for plain-speaking citizen candidates.
Born in Memphis, Tennessee, and raised in Atlanta, Mr Cain is the son of a chauffeur and a maid. He attended historically black Morehouse College, earned a master's degree from Purdue University and worked as a mathematician for the Navy before beginning to scale the corporate ladder.
He worked at Coca-Cola, Pillsbury and Burger King before taking the helm of the failing Godfather's Pizza franchise, which he rescued by shutting hundreds of restaurants.
He burst onto the political stage when he argued with President Bill Clinton over the Democrat's health care plan at a 1994 town hall meeting.
"On behalf of all of those business owners that are in a situation similar to mine," asked Mr Cain, "my question is, quite simply, if I'm forced to do this, what will I tell those people whose jobs I will have to eliminate?"
In his speech, Mr Cain said the American dream is under attack from runaway debt, a stagnant economy, a muddled foreign policy and an influx of illegal immigrants.
"It's time to get real, folks. Hope and change ain't working," he said. "Hope and change is not a solution. Hope and change is not a job."