Radio talk show host and former Godfather’s Pizza chief executive Herman Cain formally announced Saturday that he is joining the race for the 2012 Republican presidential nomination.

“I’m running for president of the United States, and I’m not running for second,” Cain told a rally in his home town of Atlanta.

His bid is a long shot. The latest Gallup poll shows only 29 percent of Republicans know who he is, and he has never held elective office. His only previous experience as a candidate was losing a GOP primary for a U.S. Senate seat in Georgia seven years ago.

But Cain is a compelling speaker who has built an enthusiastic following in some conservative circles, including among members of the tea party movement.

After the first GOP candidate debate this month — which most of the leading contenders skipped — Cain was declared the winner by a focus group that pollster Frank Luntz conducted for the debate’s sponsor, Fox News Channel.

He first caught national attention in 1994 when he confronted President Bill Clinton at a nationally televised town hall on health care. Cain challenged the president’s assertions that the Clinton health-care plan — which ultimately went down to defeat — would be affordable for businesses and their workers.

The announcement video on Cain’s campaign Web site draws heavily on Cain’s biography as the son of a father who left his farm at 18 “with just the clothes on his back” and a mother who worked as a domestic. In it, he recounts his cancer battle and his business experience turning around the fortunes of the pizza chain.