After months on the sidelines, Rick Santorum finally gets his chance at center stage in a debate of Republican candidates on Wednesday, and the increased scrutiny that comes with it.
Santorum is surging in opinion polls and is likely to face tough questions over some of his strong social conservative views when he, Mitt Romney, Newt Gingrich and Ron Paul gather for the 8 p.m. EST (0100 GMT Thursday) debate sponsored by CNN.
With March 6 "Super Tuesday" contests approaching, it may be the last major opportunity for all the candidates to make their case before a national audience on why they should be the Republicans' choice to face Democratic President Barack Obama in the November 6 election.
Former Massachusetts Governor Romney, suddenly finding himself chasing Santorum after seemingly running as the inevitable nominee, needs a breakthrough performance to halt the former Pennsylvanian senator's surge and restore luster to his own campaign.
Santorum needs to build on his momentum going into the Arizona and Michigan primaries on February 28 and pave the way for Super Tuesday, when 10 states hold contests.
"For Santorum, there are a lot of expectations," said Republican strategist Ron Bonjean. "Now that he has reached the superstar status, he has to perform very well. Any stumble by Santorum will be magnified because of his front-runner status. He's going to have to face these attacks head-on."
Santorum leads Romney in Michigan opinion polls and is catching up in Arizona where a Time/CNN poll on Tuesday found Romney ahead by just 36 percent to 32 percent.
Former private-equity executive Romney is likely to attack Santorum over approving spending bills during his years in the Senate until he was voted out in 2006.
Santorum was on the defensive in Arizona on Wednesday about his time in Congress.
"We went there and we exposed scandal after scandal - bi-partisan scandal, bi-partisan scandals where Republicans and Democrats were doing things to undermine the credibility of Washington, D.C.," he said.
What Happened to Gingrich?
Gingrich, himself a former front-runner who has a strong record in debates, has dropped in polls since Romney surprisingly got the better of him in two televised encounters in Florida last month.
The Republican race has been the most chaotic in decades as many conservatives have sought to find someone other than Romney, who made his name in politics in heavily Democratic Massachusetts, as their candidate.
Gingrich, Rick Perry, Herman Cain, Michele Bachmann all had their time in the limelight as the Romney alternatives, only to tumble away. Twenty previous debates have been crucial in determining who stays on top and who drops.
Now it is Santorum's turn.
In recent days his views against birth control and in favor of home schooling over public schools have drawn huge media attention. He has questioned Obama's "theology," and suggested that the president's healthcare law encouraged abortion by requiring insurers to cover various prenatal tests used to identify abnormalities.
The back-and-forth on social issues has detracted from Republican attempts to keep the U.S. economy as the central focus of the campaign and provided the Democrats ammunition to pronounce the Republican field as out of step with mainstream Americans.
Romney is expected to release details of a tax reform plan on Wednesday ahead of the debate. He said on Tuesday that he wants a flatter, simpler tax system.
Romney's struggle has given voice to some in the Republican establishment who may want to draft a latecomer to the 2012 race out of concern that nominating Santorum would make Obama's re-election far easier.
The pressure is on Romney to raise questions about Santorum's electability. Santorum has Romney on the run in Michigan, where Romney was born and his father was governor, and a loss there could be devastating.
"The outcome of the debate will be an indicator of whether or not the Republican establishment will be closer to hitting the panic button," Bonjean said.