SOUTHFIELD, Mich.  -- Struggling to keep his presidential bid going after two second-place finishes, Mitt Romney on Sunday focused on his Michigan roots and promised to do more to lift up the economically hard-hit state than rival John McCain. He also suggested another rival, Mike Huckabee, was the wrong type of Republican for the nomination.

"I will commit this to you," Romney said Sunday, nearly yelling himself hoarse during a boisterous rally with more than 500 people at Lawrence Technical University. "If I'm president of the United States, I will not rest until Michigan is back, and I will bring it back with your help. Together, we'll do it."

Michigan has been reeling from the U.S. auto industry's downturn; the state has the nation's highest unemployment rate at 7.4 percent.

Romney traveled with his wife, Ann, who also was born in Michigan, and talked about meeting her in the basement of Cindy White's house in Birmingham, Mich. He recalled his summer vacations on Torch Lake, and days ago visited the Statehouse to pose beneath the portrait of his late father, George, a three-term governor, in the Capitol rotunda.

"What a thrill it is to come back to Michigan, where the skies are cloudy all day, trees are just the right height, almost all the cars are American made -- the way they ought to be," he said Sunday to cheers from the knowing audience. "Of course, people speak with no accent, and they know that `pop' refers to a drink, not a relative, and, of course, Vernors is the best ginger ale in the world."

Critics point out that while George Romney was a popular figure, he last ran for office in 1966 -- more than 40 years ago. The elder Romney failed in a 1968 campaign for the presidency, and his wife, Lenore, lost a 1970 U.S. Senate campaign in Michigan.

In addition, Romney's older brother, Scott, lost the GOP primary for attorney general in 1994, while his former sister-in-law, Ronna, lost two U.S. Senate bids, including a 1994 campaign when she, too, lost the Republican primary.

Mitt Romney and McCain, the New Hampshire winner, were statistically tied in a Detroit News poll released Sunday, but Romney led McCain by 5 percentage points in a similar survey by the Detroit Free Press.

Romney has promised to promote a revitalized transportation sector with research dollars, better trade deals, negotiated fuel-efficiency standards and a tax-free savings plan for people making $200,000 or less.

"I'm going to fight for every single good job. We're going to rebuild this industry, we're going to make Michigan strong and a leader again in the world," he said at Lawrence Tech.

Earlier in the day, Romney dismissed any suggestion he would leave the race if he did not win Michigan.

"We're going all the way through February 5th. No ifs, ands or buts about it," he said on CBS's "Face the Nation." "This is a race that is not going to be decided by a few states. It's a race that I'm taking to the nation."

He also questioned the viability of Huckabee, the Iowa caucus winner, citing the former Arkansas governor's record on taxes, illegal immigration and prison commutations.

"This is not the kind of Republican that you'd expect to go to the White House," Romney said. "This is not the kind of Republican that I think people expect as somebody who is going to lead our party."