Sen. Bob Casey (D-Pa.) will endorse Sen. Barack Obama (D-Ill.) for president later today, The Associated Press is reporting. Casey’s endorsement, in advance of the state’s pivotal April 22 primary, could help halt some of the momentum that Obama’s rival for the Democratic presidential nomination, Sen. Hillary Rodham Clinton (N.Y.), has built up in the state. Polls in the Keystone State have shown Clinton ahead by at least a dozen points, and she has the institutionally significant support of Gov. Ed Rendell (D) and the mayors of Philadelphia and Pittsburgh. But Casey is an influential figure in the state, especially with Catholic voters and conservative, working-class Democrats. His father was a popular governor in the 1980s and ’90s who often clashed with former President Bill Clinton, particularly over the issue of abortion rights. While Sen. Clinton is favored to win the Pennsylvania primary, Obama continues to lead in the delegate count and is clearly hoping to limit her ability to make gains with just 10 more states set to vote before the Democratic National Convention in late August. — Josh Kurtz