NEW YORK (AP) -- Pennsylvania Sen. Bob Casey plans to endorse Democrat Barack Obama Friday, a move that could help the presidential candidate make inroads with white working-class voters dubbed "Casey Democrats" in the Keystone State.
Campaign spokeswoman Jen Psaki said the endorsement will come as Obama begins a six-day campaign swing through Pennsylvania.
Pennsylvania's April 22 primary is the next big prize in the drawn-out nomination battle between Obama, the Illinois senator, and Sen. Hillary Rodham Clinton of New York. Clinton, who holds a double-digit lead in Pennsylvania polls, needs a victory in the state to keep her nomination fight alive.
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.
Pennsylvania has an estimated 3.8 million Catholics, or just over 30 percent of the state's population, and the percentage among Democrats is estimated to be slightly higher.
Obama's team hopes that Casey will help narrow Clinton's huge lead among white working-class voters - men in particular. Clinton routed Obama among that demographic in Ohio and Texas on March 4, raising questions about his electability in November. In recent weeks, Obama has stressed economic issues important to the middle class, and he is outspending Clinton on television advertising that features blue-collar imagery.
Clinton and her supporters have been making their own direct appeals: backers Kathleen Kennedy Townsend and Robert F. Kennedy Jr., last week wrote a letter to Pennsylvania Catholics emphasizing her plans on health care, mortgage foreclosures and fuel costs. Clinton has been endorsed by Pennsylvania Gov. Ed Rendell, giving her access to his potent political operation.
Casey's move could be seen as a political jab at the Clintons. Bill Clinton was the Democrats' presidential nominee in 1992 when Casey's father was not given a prime-time speaking position at the party's convention, which outraged many of the state's conservative Democrats.
Casey is scheduled to join Obama in Pittsburgh Friday and campaign with him as Obama travels by across Pennsylvania by bus.
The bus tour will feature "listening sessions," a technique Clinton used in her 2000 Senate campaign to convince skeptical New Yorkers that she was not just a carpetbagger looking for a plum post after leaving the White House.
Though trailing in the state, Obama hopes to prevent Clinton from racking up a large win in the state which could eat away at his delegate advantage and give her new life in the final primaries running to June.
It may be a tough sell for some in the state, which has a sizable elderly population. In the previous primaries, older Democrats have favored Clinton, while younger voters tend toward Obama.
Casey served two four-year terms as state auditor general. He lost a 2002 gubernatorial bid in the Democratic primary to Rendell.
Casey was elected to the Senate in 2006, defeating conservative GOP incumbent Rick Santorum. Obama campaigned for Casey, but so did Clinton and her husband.