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Mitt Romney is hoping to become unstoppable after a presumed victory in Florida Tuesday night, but don't count out his opponents, particularly the dark horse in the race, Rick Santorum, who's polling a far-back third nationally but has seen his support rise with Newt Gingrich's recent struggles.

Santorum, who decided to forego Florida, is spending his time in other states, returning to the trail Monday for a schedule that included Missouri, Minnesota and Colorado, and saying he's not bailing on a race where delegates are divvied up, rather than winner-take-all.

If Santorum outperforms in the polls in Florida, it would help him make the case that he's a better challenger than Gingrich against President Obama. But even without the vote, Santorum said he's not only the true conservative, but the one who knows how to win in a swing state.

"I've done it, I've done it repeatedly, and that's the kind of candidate who has a positive uplifting message, who isn't out there attacking each other on personal stuff, that's gonna get this nomination won," the former Pennsylvania senator told Fox News, speaking from Sioux Falls, S.D., where he held a quick event after being in Laverne, Minn., the night before.

Minnesota holds its primary next week and will award 40 delegates. Missouri has a primary next week but its 52 delegates aren't selected until caucuses in a month. Nevada has its caucuses this weekend and 28 delegates to allocate. Colorado's caucuses, which award 36 delegates, are next week.

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    By all accounts, even if Romney were to seal the deal optically with a victory in Florida, he won't win 1,144 delegates -- 50 percent plus one -- to secure the nomination until at least April.

    Santorum noted that Tuesday's vote in Florida is only the fourth of more than 50 to be had, if one's counting the four U.S. territories, which have nine delegates each. He said all of them will have delegates to designate to the national convention in Tampa in August.

    "This is a long way to go ... let's take our time, let's make sure the best candidate rises up," he said.

    He added that he went to Minnesota because the state's primary results matter.

    "People are going to go out to vote. People are always looking at what the polls say. The best poll is folks you know in one of the most important states in the country in the general election is going to speak, and they're going to speak very loudly, and that's why I was in Minnesota."

    The strategy is not far from rival Ron Paul's, who is also concentrating his energy outside of Florida, appearing Tuesday in Ft. Collins, Colo., as well as Denver, where a raucous crowd cheered on the Texas congressman.

    Paul told Fox Business Network on Monday that he doesn't get the same media coverage as the other candidates because he doesn't represent the "status quo." Other times, his campaign gets coverage but the pundits mock it and say he is "too extreme."

    "Of course, we've come to the conclusion that the extremists have been in charge," he said, noting that when he gets his message straight to the people, he gets a good reception.

    Paul said he also picked up support when Rick Perry and Herman Cain left the contest.

    "He had a little bit more legitimacy about being Tea Party, because he had not been in government, and you know, his arguments were a little bit more credible. So, our percentages, that's when they took a nice little jump," Paul said.

    But poll numbers do help frame the debate over invincibility, and with Romney holding a double-digit lead in Florida, and a strong position in national polls, as well as having considerable money in the bank, knocking him off his perch will be hard to do.

    That's why Gingrich has repeatedly suggested that Santorum get out of the race, saying that between the two of them, they poll better than Romney.

    But Santorum said that's not happening, and Gingrich shouldn't even ask.

    I don't think people should be telling other folks to get out of the race and get out of my way. If you want to run a race, run a race, you don't ask someone to quit just because because you think you're the better candidate. I think I'm the better candidate but Newt has every right to run," he said.