Sen. Arlen Specter’s recent party switch rocked the Senate, jolted the line of seniority within the Democratic Conference and changed the dynamics of next year’s Pennsylvania Senate race.

But for Specter’s home-state colleague, Sen. Bob Casey (D), it’s business as usual.

“Well to a certain extent it doesn’t change much at all,— Casey said. “We’re kind of chatting about what’s happening in Pennsylvania all the time, not so much about the party switch.—

In the two weeks since Specter announced he was joining the Democratic Party, Casey attended a Foreign Relations Committee hearing on piracy, introduced a pair of bills that would expand funding and access to child care, and hosted a group of constituents whose photographs on poverty in Philadelphia were displayed in the Russell Senate Office Building.

“He’s been doing what was set in motion before the switch,— Casey spokesman Larry Smar said.

One Pennsylvania Democratic consultant described Casey, elected in 2006, as “the consummate team player— and “someone who doesn’t need to have the spotlight,— while adding that Specter has long maintained a reputation for fiery outbursts.

Still, Casey has enjoyed a friendly working relationship with Specter, who spent 28 years in the Senate as a Republican. Specter’s political career even overlapped with Casey’s father, the late Pennsylvania Gov. Bob Casey (D).

And while Specter and Casey have often been on opposing sides politically — Specter campaigned against Casey in 2006 — Casey is now ready to do whatever it takes to help Specter win re-election next year as a Democrat.

“I’ve known him since he was a young man, [and] the relationship has always been excellent,— Specter said of Casey. “He’s an experienced campaigner, so his advice and help is very important.—

Specter is facing a potential challenge from Rep. Joe Sestak (D) in the primary, and he finds himself breaking new ground among a different voting base in Pennsylvania. Undoubtedly, he will have to rely on his new Democratic colleague to help build political goodwill with the state’s Democratic establishment.

“If Specter is going to be challenged by Joe Sestak, he’s going to need Casey,— the Pennsylvania-based consultant said, adding that because of the party switch, “their working relationship has now gone to a completely different level.—

“There’s still a good number of Democrats that will want to talk about this whole process,— Casey said of the undecided voters taken aback by Specter’s decision to defect to the Democratic ranks.

“The ultimate goal is to achieve unity and consensus with two Democratic Senators. I had already said that I will support Sen. Specter, [and] I’m happy to give campaign advice,— Casey added.

Specter will need that counsel perhaps nowhere more than with Pennsylvania’s labor unions. Specter, a longtime moderate, dealt a heavy blow to the unions in March when he voiced his opposition to a bill that would make it easier for workers to unionize. His position on the “card check— bill greatly diminished the chances of it clearing Congress this year.

Unions have a strong presence in the Keystone State and strongly backed Casey in 2006. As labor leaders scramble to strike a compromise that could pass Congressional muster this year, Specter could find himself working to rebuild ties with a critical political ally for 2010.

“We believe Sen. Casey will be a tremendous asset to Sen. Specter and [the two] will work closely together as a powerful team,— Democratic Senatorial Campaign Committee spokesman Eric Schultz said.