SOMERSET, Pa. (AP) - Former Pennsylvania Sen. Rick Santorum, a blunt talker who is popular among social conservatives, plunged into the 2012 Republican presidential sweepstakes Monday, saying he wants to protect American freedoms under threat from President Barack Obama.

Once the No. 3 Republican in the ranks of the Senate GOP leadership, Santorum charged that Obama has worked to undermine Americans' liberties and has imposed a national health care plan that saps individual choice. He accused Obama of spending billions of dollars that will add to the debt of future generations and said the president lacks faith in the nation's potential.

"I'm ready to lead. I'm ready to do what has to be done for the next generation, with the courage to fight for freedom, with the courage to fight for America," Santorum said, speaking the sun-splashed steps of a county courthouse in western Pennsylvania. "That's why I'm announcing today that I'm running for president of the United States of America."

Santorum, who enjoys strong support from the anti-abortion rights bloc in the Republican Party, nodded to the social conservatives who have huge sway in early nominating states of Iowa and South Carolina. He also pitched himself to tea party-style activists who have yet to jell around a single candidate.

"The principal purpose of America was to make sure each and every person was free. Ladies and gentlemen, that is at stake now," Santorum said, pointing to a Democratic-pushed health care law that conservatives loathe.

"Every single American will be hooked to the government with an IV," Santorum said.

Santorum enters the race four days after former Massachusetts Gov. Mitt Romney formally declared his candidacy and former Utah Gov. Jon Huntsman and Minnesota Rep. Michele Bachmann are strongly weighing bids.

Former House Speaker Newt Gingrich, former Minnesota Gov. Tim Pawlenty and businessman Herman Cain are already in a race that has seen some of its biggest names decide against bids.