SOMERSET, Pa. — Former Pennsylvania Sen. Rick Santorum, a blunt talker who is popular among social conservatives, plunged into the 2012 Republican presidential race Monday, saying he wants to protect American freedoms under threat from President 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 on 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.”