Pennsylvania Sen. Bob Casey is endorsing Democrat Barack Obama.
Casey said Friday at a boisterous rally, "I believe in my heart that there is one person whose uniquely qualified to lead us in that new direction and that is Barack Obama."
The two appeared on the stage together.
Pennsylvania's April 22 primary is the next big prize in the drawn-out nomination battle between Obama and Sen. Hillary Rodham Clinton of New York.
Casey is a first-term senator and the son of a popular former governor of the state. Casey is Catholic and, like his father, is known for his opposition to abortion and support of gun rights. His support could help Obama make inroads among Catholic voters.