SPECTER’S FUTURE…. When Arlen Specter issued a statement yesterday, explaining his party switch and announcing his intention to seek re-election as a Democrat, he acknowledged that he might be trading one primary fight for another. “I am ready, willing and anxious to take on all comers and have my candidacy for re-election determined in a general election,” Specter said.

For his sake, I hope Specter realizes that some of these “comers” might be Democrats.

Rep. Joe Sestak (D-PA) is known by some to be very ambitious. Perhaps some of that ambition was showing when he said today that he was going to “wait and see” on whether he’d support Republican-turned-Democrat Arlen Specter in a Democratic primary.

Sestak, a former two-star admiral elected in 2006, thought to be considering a 2010 Senate bid of his own, called Specter’s decision a “good thing” for Specter, but not necessarily for Democrats or Pennsylvanians…. “I’m going to have to wait,” Sestak said on whether he’d support Specter. “If the alternative is Toomey, that’s one issue.”

Sestak not only sounded like a likely candidate, he even started sounding out some themes voters might hear in a primary. He told NBC’s Andrea Mitchell, “I ran for something, not against something,” adding that people should ask of Specter, “What he’s running for?”

What’s more, it’s not just Sestak. Joe Torsella, former head of the National Constitution Center, was, up until 24 hours ago, the only officially announced Democratic candidate running for the Senate in Pennsylvania. A couple of hours after Specter’s announcement, Torsella said he still has every intention of staying in the race.

Based on what we heard yesterday from party leaders — the White House, DSCC, DNC, et al — Specter will enjoy the support of the Democratic establishment. I suppose it’s a courtesy (and a luxury) extended to all Democratic incumbents seeking re-election, even if the incumbent hasn’t been a Democrat for very long.

But the party obviously can’t force other Democrats to skip the race, and Specter’s decades of service as a Republican — and former George W. Bush ally — may give pause to more than a few Pennsylvania Democrats. (Yesterday, Specter said, “I don’t expect everybody to agree with all my votes. I don’t agree with them all myself at this point.” Expect to hear a lot of this.)

And just to complicate matters, let’s also not forget the other side of the aisle. The GOP primary was poised to be a contest between Specter and Pat Toomey. Just because Specter has left the party does not mean Toomey is the presumptive Republican nominee. On the contrary, plenty of Republicans who might have been interested in the race, but stayed away out of deference for Specter, might now give the race another look. Pay particular attention to former DHS Secretary and former Gov. Tom Ridge (R), who’s about to get the hard sell from Republican leaders on the Hill.

It’s obviously still very early, but I wouldn’t be shocked if neither Specter nor Toomey were on the general election ballot in November 2010.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.