Mitt Romney scored two big primary victories Tuesday in Michigan, the state where he was born, and in Arizona, solidifying his claim to be the front-runner in the race for the Republican presidential nomination.
Romney led chief rival Rick Santorum, the former Pennsylvania senator, by more than 30,000 votes with nearly all precincts counted from across Michigan. Two other candidates, Texas Rep. Ron Paul and former House speaker Newt Gingrich, put up little effort in Michigan and were running well behind the two leaders.
"We didn't win by a lot but we won by enough, and that's all that counts," Romney told cheering supporters in Novi, Mich., referring to that state's close outcome as "a great victory."
Michigan was a must-win state for Romney, given his historic ties to the state. Although he is the former governor of Massachusetts and maintains a home in California, Michigan is where he grew up and where his late father was governor.
Santorum, in a speech delivered as news organizations were declaring Romney the winner, declared the results a boost for his candidacy nonetheless because of Romney's advantages and personal ties in Michigan.
"We came into the backyard of one of my opponents, in a race everyone said ... 'You really have no chance here,' " Santorum said. "All I have to say is, I love you back."
Heading into the voting, polls showed Michigan was too close to call, but Romney had a comfortable lead in Arizona polling.
Paul has not made a strong challenge in either state. Gingrich was focused on the 10 Super Tuesday states holding contests next week, among them his home state of Georgia.
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Romney won the Michigan primary in 2008 over eventual nominee John McCain. Romney had the strongest organization in the state this time around, too, and he reminded voters of his roots and claimed the experience needed to improve the economy.
But as in other states, Romney had difficulty finding a campaign voice and was plagued by missteps and statements that underscored his own background of wealth and privilege. His Michigan roots were undercut to an extent by unease with his candidacy among the party's most conservative voters and his record of opposition to the federal bailout that led to a revival of Detroit's auto industry.
Santorum has been riding a wave of support from his more conservative base - a bloc of voters that may be far more excited about getting out to vote.
A poll of voters leaving voting places in Michigan showed Romney doing well with older and college-educated voters. Santorum, who emphasized social issues, did well among voters who called themselves "born-again" Christians, and among voters who identified themselves as very conservative or supporters of the Tea Party.
Returns from Michigan demonstrated the closeness of the battle between the two frontrunners. Romney led in the southeastern counties around Detroit, and in some northern counties along the Great Lakes. Santorum held leads in a wide range of rural sections, including the Upper Peninsula, and in the traditionally conservative Republican western part of the state. In rural Huron County, atop the "thumb" of Michigan's mitten-like shape, Romney won in complete but unofficial returns by just 4 votes out of nearly 4,000 cast in the county.
A majority of voters, according to the exit polling, listed the economy as their top issue, followed by the federal budget deficit, and Romney had the edge among both groups. Santorum won overwhelmingly among the one in seven voters who saw abortion as the top issue.
Santorum confirmed that he had targeted Michigan Democrats with automated phone calls encouraging them to vote against Romney.
"We're going to get voters that we need to be able to win this election. And we're going to do that here in Michigan today," Santorum said Tuesday.
Michigan Democratic Party Chairman Mark Brewer said the party was not encouraging Democrats to cross over and vote in the Republican primary, which state law permits. He said Santorum was "inviting" Democrats to vote for him on the GOP ballot.
"I don't think it's going to be a big deal," Brewer said, adding that Romney's "problem is not a few Democrats crossing over."
Each of Michigan's 14 congressional districts awards two delegates to the winner of the district. Two other delegates are awarded by the proportion of the vote won statewide.
Arizona, by contrast, is a winner-take-all state. Romney was endorsed by most of the state's top politicians, including Gov. Jan Brewer and Sen. John McCain.
A candidate needs 1,144 delegates to secure the GOP nomination. Romney is leading with 163 delegates followed by Santorum with 83, according to an Associated Press tally.
Kucinich reported from Novi, Mich.; Welch reported from Los Angeles; Contributing: Catalina Camia, USA TODAY; Todd Spangler, Kathleen Gray, Zlati Meyer and Dawson Bell, Detroit Free Press; Associated Press