Now, meet your likely primary challengers:

Rep. Joe Sestak, who’s been a prolific fundraiser, is considering defying party leaders and running against Specter despite Tuesday’s hoopla, though he told FOXNews.com on Wednesday, “I have not made up my mind on it.”

Sestak, a second-term House member, is basing his decision on what Specter may do or say in the coming days. Sestak said he wants to hear Specter make his case to Pennsylvania voters about why Specter now should carry the banner for Democrats after representing the Keystone State as a Republican for 29 years.

Sestak released a critical statement about Specter’s switch from the GOP back to Democrat (where he originally started) Tuesday:

“This shows the principle rule of politics: tomorrow is always another day — as today was. This may be good for Arlen, politically; however, two key questions need to be answered. First, after 31 years in the military, I learned that you run for something, not against someone. Arlen has made a decision to leave a race because he could not win against someone. What needs to be known is what he is running for. Second, I watched then-Gov. Clinton and then-Sen. Obama take a leadership position in the Democratic Party and shape it. The leadership that would have been most impressive would be if Arlen had used his role to reshape the Republican Party that he said he had entered when it was a “big tent,” but now is leaving because it has gotten too small. In short, I believe that the principles of what he is running for and his commitment to accountable leadership are questions that still need to be addressed.”

Another potential challenger to Specter is Pennsylvania Board of Education chairman Joe Torsella, previously an aide to Gov. Rendell. Torsella, who has already raised nearly $600,000 in campaign cash, released a statement of his own Tuesday. It doesn’t sound like he’s willing to play second fiddle to anyone, Specter included:

“I decided to run for the United States Senate from Pennsylvania for one simple reason: I believe we need new leadership, new ideas and new approaches in Washington. Nothing about today’s news regarding Sen. Specter changes that or my intention to run for the Democratic nomination to the Senate in 2010 — an election that is still a full year away.”

It will be interesting to see if Rendell can persuade either of the two potential primary opponents to back out of the race. His defection was not quite jumping from the frying pan into the fire, since Specter was certain dead meat if he had remained with the GOP. But the couple of Joes he may have to battle to retain his Senate seat don’t appear ready to go quietly into the night.

Play ball!

- JP