Former Pa. Sen. Rick Santorum enters 2012 GOP presidential race

SOMERSET, Pa. (AP) — Former Pennsylvania Sen. Rick Santorum, once the No. 3 Republican in the Senate, said today he's seeking the GOP nomination for president, vowing he's "in it to win."

Santorum, a favorite among his party's social conservatives, chose to confirm his plans during an appearance this morning on ABC's "Good Morning America" at the balloon-draped site he chose in the western Pennsylvania coalfields for his formal announcement.

He has enjoyed strong support in the past from the anti-abortion rights bloc in the Republican Party, and he enters the race four days after former Massachusetts Gov. Mitt Romney formally declared his candidacy.

Speculation remains strong that former Utah Gov. Jon Huntsman and Minnesota Rep. Michele Bachmann will jump into the race along with former House Speaker Newt Gingrich, former Minnesota Gov. Tim Pawlenty and businessman Herman Cain and, who already are in.

Former Arkansas Gov. Mike Huckabee, Mississippi Gov. Haley Barbour, Gov. Mitch Daniels of Indiana and entrepreneur-entertainer Donald Trump have said they're not running. There also has been speculation that former New York Mayor Rudy Giuliani, who sought the nomination in 2008, is considering making another run.