LANSING, Michigan — The stakes are high for Mitt Romney in Tuesday's Michigan primary where a loss in his home state would badly tarnish his image as the inevitable Republican presidential candidate and commit him to a long march to the nomination that could work to President Barack Obama's advantage.
A victory Tuesday by rival Rick Santorum would be a public-relations nightmare for Romney, who was born and raised in Michigan where his father once served as governor. But Romney's campaign still would carry on with more money than any of his Republican rivals and remain better organized to compete to the end.
Santorum, a former Pennsylvania senator, is riding a wave of momentum after winning Feb. 7 caucuses in Minnesota, Colorado and a nonbinding primary in Missouri. But a lackluster debate performance on Wednesday seems to have halted Santorum's surge.
Polls in Michigan show a dead heat between Romney and Santorum, who is playing up his working-class background as the grandson of a Pennsylvania coal-miner as a contrast to the multimillionaire Romney, the former head of a private equity firm.
"This race is close. This race is winnable. But you've got to want it," Santorum told supporters of the limited government, anti-tax tea party movement in St. Clair Shores.
With a Michigan victory, Santorum could solidify his place as a real threat to Romney, a former Massachusetts governor, heading into Super Tuesday, the 10-state sweepstakes on March.
Obama stands to gain from a drawn-out Republican nominating race that forces the contenders to focus their appeals on issues dear to the party's conservative base rather than reach out to independents, Obama has been most vulnerable on his handling of the economy, but signs are growing that the recovery from the Great Recession is picking up speed and Obama now leads in most polls against all his would-be rivals.
In the final weekend of campaigning before Tuesday's Michigan and Arizona primaries, Romney focused on central and southeast Michigan's urban and industrial centers in hopes of pulling ahead of Santorum.
While Romney kept most of his attention on the Democratic incumbent, he also worked to lay doubt about the core principles of his lightly funded main Republican rival.
Romney is the one facing stubborn doubts from some conservatives for his changed positions on social issues such as abortion, but he tried to portray Santorum, a former Pennsylvania senator, as a Washington insider with cracks in his own conservative credentials. Santorum called such criticism "laughable."
A crowd in Lansing heard Romney accuse Santorum of caving to party leaders on issues he opposed, including financing Planned Parenthood whose women's health services include birth control and abortions.
"This is not time for lifelong pols who explain why they voted for this or that based on what they were asked to do by their fellow colleagues," Romney told about 300 activists gathered for breakfast at a country club. "I will be a president of principle."
Romney tried to undermine Santorum's profile as an abortion opponent by noting Santorum's backing in 1996 of fellow Pennsylvanian Arlen Specter in the Republican presidential race. "He supported the pro-choice candidate," Romney told more than 2,000 at a forum in Troy put on by a tea party umbrella group. Santorum spoke to the group, Americans for Prosperity, earlier Saturday.
Santorum, who has portrayed himself as a loyal conservative and is popular among evangelical conservatives, ridiculed Romney's claims.
"It is absolutely laughable to have a liberal governor of Massachusetts suggest that I am not a conservative," Santorum said to cheers to the same group. "He repeatedly gets up and says all these things that he didn't do that he did do. Folks, this is an issue of trust."
Santorum compared the health care bill Romney signed in Massachusetts in 2006 with the reform bill Obama signed in 2010. The federal program is wildly unpopular with conservatives.
"Are you going to vote for someone that says one thing one day anything else the next day that's necessary to win? Or are you going to vote for someone you trust?" Santorum asked the crowd in Troy.
The volleys over principle and loyalty punctuate the all-out two-man race in Michigan, leaving behind the two others in the field. Both candidates are spending heavily on television advertising, although the better-funded Romney was laying out more.
Libertarian-leaning Texas Rep. Ron Paul is hardly a factor in Michigan but is airing advertisements criticizing Santorum, which aids Romney. Paul was campaigning in Oklahoma earlier Saturday before making a stop at Central Michigan University in Mount Pleasant.
Newt Gingrich, the former speaker of the House of Representatives, has acknowledged that he has no shot in Michigan or Arizona and has predicted Romney will win. Gingrich is betting heavily on Georgia, the state he represented in Congress, and a strong showing in another southern state, Tennessee, on March 6.
On Saturday, Gingrich was in California for the state Republican convention. He forecast a drawn-out campaign that would give a voice to late-voting states like California, which holds its primary on June 5.
Santorum is pinning his hopes for victory in Michigan on strong support from evangelicals who share his social conservative values in opposing abortion rights and gay marriage. A Roman Catholic, he is a beneficiary of more than two decades of cooperation between conservative Protestants and Catholics who set aside theological differences for the common cause of the culture war.
An Associated Press-GfK survey conducted from Feb.16-20 found Santorum leading Romney among white evangelicals, 44 percent to 21 percent. White Catholics also preferred Santorum, 38 percent to 29 percent, in the AP-GfK poll.
Romney struggles with social conservatives not only because he once supported legalized abortion, which he now condemns, but also from distrust of Mormon teaching among some evangelical Christians.
Even if Santorum beats Romney in Michigan, Romney will emerge with a healthy share of delegates Tuesday to add to his lead in the count. Romney is heavily favored to win Tuesday's Arizona primary, and claim all 29 delegates at stake. In Michigan, most of the state's 30 delegates are awarded two at a time to the winner in each of the state's 14 congressional districts.