Santorum's rocky ascendency to the national stage

Five days before Michigan's Republican presidential primary, a new American Research Group poll shows former Massachusetts Gov. Mitt Romney has lost his small lead in his birth state to rival Rick Santorum.

Santorum now leads Romney by four points - 38 percent to 34.

Rick Santorum has won three of the past four primaries and caucuses. And he's currently the frontrunner in national polls of Republican voters.

CBS congressional correspondent Nancy Cordes reports on Santorum's rise on the national political stage and how it all began.

In his first debate as the national frontrunner, Rick Santorum and his fiscally conservative credentials came under heavy scrutiny.

"While I was fighting to save the Olympics, you were fighting to save the 'bridge to nowhere,'" Romney said at Wednesday's nationally televised Republican debate in Arizona.

The former senator was attacked for everything from his history of requesting earmarks to his vote in favor of President Bush's "no child left behind" education law.

"He voted for it, but now he's running on the effort to get rid of it," challenged GOP rival Ron Paul.

Santorum's response was candid but did not bolster the tough, outsider image he has strived to project.

"I have to admit, I voted for that," said Santorum. "It was against the principles I believed in but you know, when you're part of the team, sometimes you take one for the team - for the leader. And I made a mistake."

Santorum came to Congress as a crusader. A 32-year-old lawyer from Pittsburgh, Pennsylvania who joined ranks with six other ambitious new House Republicans to root out corruption in Congress.

"Rick came in in 1990 and he was quote unquote one of the "Gang of Seven," said Republican Congressman Dan Burton of Indiana, one of Santorum's closet colleagues.

"We had an awful lot of members of Congress that were overdrawing their accounts, and it became a huge scandal. And so these seven made their reputations collectively by going after the bank scandal," Burton recalled.

That reputation helped propel Santorum into the Senate after just four years in the House and he quickly became an outspoken voice on social issues.

He pushed for intelligent design to be taught in schools alongside evolution and introduced a bill to ban late term abortions.

But his social positions put him out of step with his more moderate state, as he ran for re-election in 2006. And as a result he lost to Democrat Bob Casey by 18 points.

As of today, only three members of Congress have endorsed Santorum compared to 78 for Romney. It's a sign his former colleagues are still skeptical he can beat Romney, despite what the polls say.