Former U.S. senator Rick Santorum is the latest Republican to formally join the 2012 race for the White House, joining a field of candidates hoping to unseat President Barack Obama.

Speaking in his home state of Pennsylvania Monday, Santorum thanked supporters and said he is running because he has the courage to fight for America. He said President Obama has done a poor job of running the country, and he accused the president of wrecking the economy and having a weak foreign policy.

Santorum is a social conservative. He joins other prominent Republicans hoping to win their party's nomination and face Mr. Obama in November 2012. The others include former state governors Mitt Romney and Tim Pawlenty, former U.S. House speaker Newt Gingrich, and current Texas Representative Ron Paul.

The 53-year-old Santorum has made frequent trips to key election states like Iowa, New Hampshire and South Carolina. However, in a recent Gallup opinion poll, he ranked well down in the field of announced and possible Republican hopefuls, garnering just 2 percent support.

Santorum served two terms in the U.S. Senate before being defeated in his re-election bid in 2006.

Former Alaska governor Sarah Palin has not said whether she will enter the race. She was the Republican vice presidential candidate in 2008.