The specter of a primary challenge to newly minted Democrat Sen. Arlen Specter looms even larger this morning.

And the gauntlet is being thrown down right here in Delaware County.

U.S. Rep. Joe Sestak has not made it a secret that he has been less then thrilled about the way party leaders have fallen all over themselves to welcome Specter, in the process giving every indication they wanted him to be their candidate in 2010.

Sestak has consistently given indications he is not ready to join the rush by Gov. Rendell, Vice President Joe Biden and President Barack Obama to crown Specter as their candidate.

Yesterday that drumbeat got a little louder. Reports started to surface that Sestak was telling those close to him that he was running. Talking Points Memo had a hand-written letter from Sestak to close supporters indicating he was going to run. Sestak’s sister also told the Web site she expected him to get in the race.

Then Sestak told CNN last night he would challenge Specter.

The only thing left for him to do is sit down with his family, then make a formal announcement.

But Sestak left little doubt about his desire. He wants a piece of the longtime Republican senator who is actually returning to his roots in the Democratic Party.

Sestak already has amassed more than $3 million in his war chest. He’ll need a lot more to snatch the crown off Arlen’s head. He needs to seriously upgrade his visibility outside the Philadelphia region. My guess is that if you go west of West Chester, nobody has ever heard of Joe Sestak. Everyone in Pennsylvania has heard of Arlen Specter. He makes it a point in every campaign to visit every county in the state.

That doesn’t mean Sestak doesn’t have a chance. It does mean he’s facing a decidedly uphill battle, in fact a much bigger hurdle than the one posed in his historic first run for office in 2006, when he stunned the Delco political world by showing 20-year incumbent Curt Weldon the door in a bruising 7th District congressional race. In that race Sestak got a huge boost by a federal investigation of Weldon that continues to drag on almost three years later.

Sestak often says he didn’t ask for Democratic Party leaders’ blessing to get in the race vs. Weldon. Actually, on a closer look, that’s not exactly the case. Rendell was pivotal in asking the guy who appeared to be the front-runner, Bryan Lentz, to step aside to allow Sestak to assume the mantle.

Sestak probably shouldn’t hold his breath waiting for much in the way of support from party leaders. But it’s pretty clear that a fair amount of people inside the party are not all that thrilled with Specter and wouldn’t mind seeing him challenged in the primary.

Enough to snatch away the nomination? I don’t see it. But I don’t expect that to stop Sestak. He goes to the beat of his own drummer. He doesn’t exactly shy away from the limelight. And it’s not exactly a secret that the guy who once served in the Clinton Administration has his eyes on a loftier perch.

Every time I’ve ever asked him about the future and runs for other offices, he’s always replied the same way. “I love my job.”

Turns out he’d love the one currently held by Arlen Specter, too.

The only thing left is the announcement.