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Mitt Romney, after fending off Rick Santorum in his home state of Michigan, is fast-approaching the biggest test so far of his volatile front-runner status: next week’s Super Tuesday contests where 419 delegates are up for grabs.

The former Massachusetts governor charges into those 10 contests with a head of steam, after securing back-to-back victories Tuesday night in Michigan and Arizona.

The only stop along the way is the Washington state caucus contest this Saturday.

Romney will have to unleash the force of his campaign juggernaut, as his competitors are still polling strong in key Super Tuesday states.

Rick Santorum, who placed second in both contests on Tuesday, is leading in most recent polls out of Ohio. Newt Gingrich is leading in Georgia, the state he used to represent in Congress.

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The two states are the biggest delegate prizes on Super Tuesday. All four Republican presidential candidates have been mapping out a Super Tuesday plan – with some envisioning their own comeback sparkling through the prism of Super Tuesday possibilities.

Gingrich’s plan, he told Fox News, revolves around a victory in Georgia and strong showings in several other March 6 states.

Romney, though, could be looking at an easy pick-up in at least one state. He and Ron Paul are the only candidates on the ballot in Virginia, one of the 10 states holding contests a week from now.

Romney heads into those primaries and caucuses after preventing what could have been a major upset for his campaign in Michigan. His victory over Santorum hardly locks down the race, but at least for the moment it keeps the former Pennsylvania senator’s campaign in check.

"We didn't win by a lot, but we won by enough, and that's all that counts," an upbeat Romney said at his Michigan victory rally late Tuesday night.

The two-for-two performance from Romney helps him reaffirm his front-runner status among the remaining four GOP candidates. In a reflection of the night's results, the candidate kept his victory rally remarks focused on President Obama and his own candidacy, glossing over what has become a bitterly personal contest between him and Santorum in recent weeks.

He called the election a "time for choosing" in America.

"This time we've got to get the choice right," Romney said.

Romney, in his address, touted his recently unveiled tax reform plan and like the other candidates pledged to open up more U.S. land to oil and gas drilling -- at a time when gas prices are rising and becoming a more frequent topic on the campaign trail.

"Look, when it -- when it comes to the economy, my highest priority will be worrying about your job, not worrying about how to save my own," he said in a crack at the president.

The former Massachusetts governor will take all 29 of Arizona's delegates. With 100 percent of precincts reporting in the state, Romney was leading Santorum 47-27 percent. Gingrich came in third, while Paul placed last in the state.

Unlike in Arizona, though, Romney will end up sharing Michigan's 30 delegates with Santorum in the relatively close race.

Romney received 41 percent of the vote in Michigan, followed by Santorum with 38 percent. Paul placed third in the state, followed by Gingrich.

The Michigan election was not originally expected to be as close as it was. For weeks, Romney seemed poised to walk away with well-timed victories in the two contests Tuesday night.

Romney, while popular in Arizona, has deep roots in Michigan which were expected to play to his advantage. He was born there, his father was governor there and he won the state in the 2008 GOP presidential primary.

But Santorum's surge, and a decision by the former Pennsylvania senator to compete hard in the state, put Michigan in pure toss-up territory heading into primary day. Santorum's campaign demanded attention as he went from being sidelined at debates earlier in the year to winning the Iowa caucuses by a hair in a late call, and then picking up wins in Missouri, Minnesota and Colorado all in one night.

Exit polls showed Romney and Santorum were each leading among distinct categories of voters.

Romney did well in Michigan among those who value electability and experience the most; Santorum fared best among those who most value strong moral character and true conservative values.

Fortunately for Romney, those who think ability to beat Obama is the most important quality made up 33 percent of those polled -- those who wanted someone who is a true conservative made up just 15 percent.

Santorum, though, dominated among evangelical voters, picking up 50 percent of their support. Romney picked up 35 percent. In Michigan, evangelicals made up nearly four in 10 voters on Tuesday.

The closeness of the race helped fuel a tense contest between the two candidates, with each accusing the other of being a false conservative.

Romney also slammed the Santorum campaign Tuesday for putting out a robo-call in Michigan urging Democrats to vote in the GOP race for Santorum. Romney called it a "new low" for his opponent.

But Santorum defended the robo-call, and at his post-election rally put a positive spin on the night's results.

"A month ago they didn't know who we are, but they do now," Santorum said.

Santorum claimed voters are still getting to know him, but said they'll ultimately want someone like him to "take on" Obama as he blamed the current regulatory environment for hard times in America.

"It's getting harder for people to make ends meet, because we have a government that is crushing us every single day with more taxes, more regulations, and the idea that they know better than you how to run your life," Santorum said. "That ultimately is what this race is about. It goes down to the very nature of who we are as Americans."

Gingrich and Paul barely competed in either contest being held Tuesday, and focused instead on the Super Tuesday primaries.

At a rally in Georgia on Tuesday evening, Gingrich said voters need somebody who has "really large ideas for a really large country."

In a separate interview on Fox News, Gingrich offered a rough sketch of his comeback strategy. He said he plans to win Georgia, while doing "very well" in a handful of other Super Tuesday states, victories he projected would give him momentum to win subsequent southern contests in Mississippi and Alabama.

Paul, meanwhile, pumped up a crowd of enthusiastic supporters Tuesday evening in Virginia, where he and Romney are the only GOP candidates on the ballot. He stuck to his bread-and-butter message, railing against Washington on the issues of overseas military interventions, over-spending and over-regulation.

Paul, in an interview on Fox News, argued that he can attract independents and Democrats in a general election in a way the other Republican candidates cannot.

"Somebody like Santorum doesn't do that as well," Paul said.

Nationally, Romney entered and exited the night with the delegate lead.

Before Tuesday's contests, The Associated Press count showed Romney with 123 total delegates. Santorum followed with 72. Gingrich had 32 and Paul had 19.

The eventual nominee will need to win 1,144 delegates. There are 40 delegates up for grabs in Washington's caucuses on Saturday.