DETROIT, Michigan (AFP) -- Mitt Romney hopes to avoid an embarrassing slip-up in his native Michigan on Tuesday as he looks to wrest the momentum back from surging Republican presidential rival Rick Santorum.
The state-by-state voting process that will decide which of the four remaining Republican contenders will face off against Democratic President Barack Obama in November's general election is reaching a pivotal phase.
Santorum edged out Romney in the first contest in Iowa on January 3 by a handful of votes and the two men are now locked in a head-on battle many pundits believe could go all the way to the Republicans' August convention.
Former House speaker Newt Gingrich rose to the fore after a surprise win in South Carolina but was steam-rolled by Romney in Florida and then Nevada as the former Massachusetts governor took back control of the race.
But then Santorum, a staunch Christian conservative who strongly opposes abortion and gay marriage, upset the apple cart by taking a trio of victories in one night, February 7, in Minnesota, Missouri and Colorado.
He rode that wave of support into two supposed Romney strongholds that vote on Tuesday, Michigan and Arizona, advancing in the polls by painting himself as the authentic conservative and his multimillionaire opponent as out of touch.
But Romney put in a strong debate performance when it mattered on Thursday and has used his financial muscle to successfully portray Santorum, a former Pennsylvania senator, as a Washington insider.
The latest polls show Romney has opened up a double-digit lead in Arizona, where a significant percentage of the population shares his Mormon faith and where he likely benefited from large numbers of early voters.
The outlook is murkier in Michigan, where Santorum is hoping for a major upset that will prove his trio of wins earlier this month was no fluke and which could catapult him into prime-time as a genuine alternative to Romney.
Romney was born and grew up in Michigan, where his father was governor, so a loss would be a huge embarrassment for a supposed frontrunner who has displayed a staggering inability to connect with core Republican voters.
If Santorum clinches Michigan, he could claim the momentum going into "Super Tuesday" -- on March 6 -- when 10 states vote on a pivotal day in the race to see who takes on Obama in November.
In Ohio, one of the key states voting on "Super Tuesday" and a major battleground in November, Santorum holds a seven percentage point lead over Romney, according to a Quinnipiac University poll released Monday.
Romney has talked up his chances of a double win on Tuesday, saying it would be "huge," but in reality he knows that losing Michigan would be nothing short of disaster.
At a Monday rally, Romney did not mention Santorum, instead stressing his purported business acumen, saying: "I believe you want someone who understands how to get the economy working and how to get jobs again."
The message resonated with Mike Castonia, 56, who said: "None of the social issues make a difference in the long run."
"It's about the economy, stupid," he said, paraphrasing the famous line from Democratic president Bill Clinton's successful 1992 campaign.
All four candidates have vowed to stay in the race until the party convention at the end of August, when a result might have to be brokered behind the scenes if no one reaches the magic number of 1,144 delegates.
Romney leads in pledged delegates, having won the more important states so far.
The other two candidates, former House speaker Newt Gingrich and small-government champion Ron Paul, a veteran Texas congressman, trail significantly in national polls.
The negative, gaffe-ridden slug-fest to become the Republican standard-bearer is providing ample fodder for Obama as he prepares for the November 6 election amid an improving economy and rising approval ratings.
