BOSTON — Republican presidential candidate Mitt Romney has decided to pull his advertising from South Carolina and Florida, in a sign of trouble for a campaign that badly needs a win.

Romney had been hoping to challenge John McCain and Mike Huckabee in South Carolina, and Rudy Giuliani in Florida, where the former New York mayor has been spending time and money.

"We feel the best strategy is to focus our paid messaging in Michigan," Romney spokesman Kevin Madden said Wednesday.

The decision comes on the heels of back-to-back second-place finishes in Iowa and New Hampshire for the former Massachusetts governor. Romney, a multimillionaire who had used some of his own cash, had invested heavily in both states, counting on the two to give him the momentum toward the nomination.

Romney had been spending about $280,000 per week in South Carolina and spent $3 million there last year, according to rival campaigns. In Florida, he had been spending $160,000 per week and had spent 2.5 million in 2007.

Romney won the Wyoming caucuses on Saturday, a contest that drew little attention, and is counting on a win Tuesday in the Michigan primary. Romney was born in the state and his father served as its governor.

Earlier on Wednesday, Romney had assured his top financial backers that he will win the upcoming Michigan primary, as he and his staff worked to soothe supporters unsettled by his losses in the Iowa caucuses and New Hampshire primary.

"It's just getting started," the presidential contender told hundreds of supporters gathered at a convention center for a follow-up to the "National Call Day" that raised an unprecedented $6.5 million a year ago.

He promised to carry on to Michigan, which votes Jan. 15, as well as Nevada and South Carolina, which vote Jan. 19.

The public spectacle, a rarity for the normally tightly controlled Romney political operation, included appeals for calm from a top financial backer, eBay CEO Meg Whitman, and a top political supporter, former Sen. Jim Talent of Missouri.

"To a person, we remain incredibly optimistic that we still have a chance to win this thing," Whitman told the crowd, which included everyone from Fortune 500 executives to entrepreneurs.

Spencer Zwick, Romney's national finance director, told the phone bankers: "If for some reason he is not the nominee, all those funds will be returned to the donor himself."

Talent, knocked out of office last fall, compared the unfolding campaign to 1976, when Gerald Ford and Ronald Reagan battled for the nomination all the way to the GOP convention.

"This is a transition time, really in both parties, and in transition times, countries need leaders," Talent said. "How well you do today is going to have a significant impact in the next several news cycles of how this campaign is perceived."

Associated Press Writer Jim Kuhnhenn reported from South Carolina