Then, later that month, the former Godfather's pizza CEO told a gathering in Charleston, S.C., that he was providing an "unconventional endorsement" of "the people."

"Here is my unconventional endorsement: Not a candidate seeking the nomination. Not someone that it is not running. My unconventional endorsement is the people! We the people of this nation are still in charge. That is who I am endorsing," Cain said.

Cain then appeared at a rally in South Carolina with late-night comedian Stephen Colbert, who was encouraging voters to register protest votes in the Republican primary by backing Cain.

Cain did not ask voters to support him in the vote, but did call them to join his "army of Davids" against the political goliaths who supported special interests.

The former pizza executive changed his mind again, though, by the end of January, where he threw his support behind former House Speaker Newt Gingrich three days before the Florida primary.

But as Romney continued to rack up primary wins and Gingrich's prospects faded, Cain made another shift, this time to Romney. Speaking to Fox News last month, the pizza magnate said the time had come to unite the party behind the former Massachusetts governor.

“The numbers are on Mitt Romney’s side, and yes, I am always saying, I will support whoever the nominee is, and it looks like Mitt Romney’s going to be that nominee, and we do need to get behind him,” he said.

He made that turn official Wednesday.

"I've met with him privately and now I'm telling everyone publicly, if Mitt Romney wasn't your favorite candidate for the Republican nomination, get over it," Cain said in a written statement. "We need unity to take back the White House, the Senate and keep control of the House of Representatives."

Cain has continued to campaign with Republican candidates who have signed on to support his 9-9-9 tax plan in recent months, and has hinted that he could peruse a career in media after the election.