Former U.S. Sen. Rick Santorum, R-Penn. has opened an eight-point lead over former Massachusetts Gov. Mitt Romney in a new national poll, signaling Santorum's continued popularity as a series of crucial primaries looms.

A new Gallup poll tracks Santorum's meteoric rise to the top of the Republican presidential standings. Two weeks ago, Santorum was in third place. After registering wins in Missouri, Colorado and Minnesota Santorum had climbed into a statistical tie with Romney.

Next Check-Point: Michigan Primary

Santorum's sustained rise could offer Romney a critical test in the upcoming Michigan primary. Despite Michigan being Romney's native state, Romney has fallen behind Santorum in the polls there.

Meanwhile, Newt Gingrich's numbers continue to tumble. The former Speaker of the House has seeen his favorability recede since a resounding victory in the Jan. 21 South Carolina primary, and he is now in a statistical tie for third place with Rep. Ron Paul,R-Texas. Despite having apparently ceded his alternative-to-Romney status to Santorum, Gingrich has sworn to continue his campaign.

Paul has also said he will stay in the race, suggesting on CNN's State of the Union that he could cobble together enough delegates to secure the nomination. Paul's campaign got a small boost from reports that Romney may have been improperly awarded a victory in Maine, where Paul narrowly placed second. The Maine caucus is nonbinding, but a victory could have symbolic importance for Paul.

There's every reason to believe this momentum will continue, Paul told State of the Union host Candy Crowley. Nobody actually knows the future.

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