Rising to challenge

Could this be the week Rick Santorum rises?

The former senator from Pennsylvania has been claiming that he is the better conservative alternative than Newt Gingrich to unseat Mitt Romney as the frontrunner in in the race for the GOP presidential nomination.

The next round of contests will provide Santorum with his best chance to show that voters agree. Republicans in Colorado, Minnesota, and Missouri head to caucus sites and voting booths on Tuesday, and early polls show that Santorum may give Romney a battle.

Romney and Santorum are virtually tied in Minnesota, the state that gives Santorum the best shot at his first victory since the Iowa caucus. In Colorado, Santorum is running a distant second behind Romney but is well ahead of Gingrich and Ron Paul. He also leads Romney in Missouri, where Gingrich is not on the ballot, but that state's primary will not count for delegates to the Republican convention.

Wins in Minnesota and Missouri and a second-place finish in Colorado could give Santorum reason to claim the title of Romney's biggest challenger.

According to Public Policy Polling, Gingrich has experienced a sharp drop in support since his losses last week in Florida and Nevada. Support for the former speaker of the House has declined 19 points in Colorado and 14 points in Minnesota. Meanwhile, 68 percent of Colorado voters and 72 percent of Minnesota voters say they have a favorable opinion of Santorum.

Such numbers may be why the Romney campaign unleashed its power against Santorum Monday, with Tim Pawlenty, the former Minnesota governor and former-GOP-presidential-candidate-turned-Romney surrogate, leading the offensive. During a Monday conference call with reporters, Pawlenty criticized Santorum's past support for earmarks.

"He clearly has been part of the big spending establishment in Congress and in the influence-peddling industry that surrounds Congress," Pawlenty said, referring to Santorum's 16 years as a lawmaker in Washington.

For his part, Santorum spent Monday lambasting Romney for the Massachusetts healthcare plan the former governor signed into law.

Santorum, speaking Monday in Rochester, Minn., called Romney "the worst possible person" for Republicans to select to attack President Obama's healthcare plan during the upcoming general election.

"The plan he put together in Massachusetts is, in fact, Obamacare on the state level," Santorum said. "[With] Romneycare and Obamacare, the government controls everything. Every aspect of the healthcare transaction is controlled by Massachusetts and by Washington. You show me the differentiation there on the most key issue in America today … your economic freedom."

The races in both Minnesota and Colorado could see drastic changes over the next 24 hours: 33 percent of voters in Colorado and 37 percent in Minnesota say they could change their minds before casting their ballots.

The stakes are clear for Tuesday: Multiple wins for Romney further cement his argument that he is the inevitable Republican nominee. But if Santorum claims a win, Romney versus Gingrich may become Romney versus Santorum.

Asked after his Monday speech if he enjoyed being in the center of Romney's crosshairs, Santorum had a quick reply: "I love it!"