I'm feeling a little bad today for Arlen Specter. Is that wrong?

The guy did what he had to do to save his political skin, crossing the aisle in exchange for what he thought would be a clear path to re-election. And what does he get for it? Grief, that's what. And nasty commercials from upstart primary challenger Joe Sestak, painting him as a phony and an opportunist. And the possibility that voters will dump him on Tuesday.

That's gotta hurt.

So much for my advice.

Last February in this space, I urged Mr. Specter to jump ship from the Republican Party, which had listed so far to the right he was having trouble hanging on. Why, I asked, would he want to?

Clearly, the GOP's angry core didn't like him any more. Many already saw him as a turncoat for crossing party lines in previous high-profile votes and considered his vote in favor of the Obama stimulus package to be the last straw. So why not leap before he was pushed? Become an Independent like Joe Lieberman did, or even return to the Democratic roots of his early political career?

Two months later Mr. Specter did exactly that. After 42 years as a Republican and 29 as a U.S. senator from Pennsylvania, Mr. Specter switched parties ... not because of any columnists, I'm sure, but because a wiley pol with his survival instincts simply couldn't ignore the numbers any longer.

A Rasmussen poll at the time showed him trailing uber-conservative Pat Toomey, the leading contender in the upcoming Republican primary, by 51 percent to 30 percent. Mr. Toomey had nearly beat him in the 2004 primary, and that was with George W. Bush in the White House fully supporting Mr. Specter. Now Barack Obama was president and more than 200,000 of the state's Republicans had changed their registration to Democrat. Presumably, these were the party moderates who made up Mr. Specter's base. Winning renomination under those circumstances was just too risky.

Announcing his decision, Mr. Specter said, in essence, that he wasn't leaving the GOP as much as the party had left him. It had shrunk its tent so dramatically, he said, there was no room left for him.

Mr. Specter's defection briefly gave Democrats the 60-vote Senate majority they sought. That goal turned out to be illusory, but in those first heady days, the Democratic leadership couldn't praise him -- and themselves -- enough. Mr. Obama, Vice-President Joe Biden, Senate Majority Leader Harry Reid, Pennsylvania Gov. Ed Rendell and others lined up to welcome him, and Mr. Specter reveled in the spotlight, as he is wont to do.

Meanwhile, his ex-compatriots sneered that the switch only proved their point, that he was not a real Republican.

Now the argument is over as to whether he's a real Democrat. Far from skating to the nomination on the strength of the party leadership's gratitude, Mr. Specter is facing a surge from two-term U.S. Rep. Sestak, the retired three-star admiral from suburban Philadelphia who is staking a claim as the only true Democrat in the race.

Mr. Sestak is an unapologetic liberal with a voting record to prove it. As former commander of an aircraft battle group, he has tough-guy credentials that few politicians on either side of the aisle can match. And like any good military strategist, he saw an opening and moved to exploit it.

Grass-roots Democrats did not like having Mr. Specter shoved down their throats. So, in a skillful and well-financed end run around the Democratic establishment, Mr. Sestak has been taking his case directly to the voters.

He's been making appearances all over the state and flooding the airwaves with ads that contrast their voting records, showing his own as far more in line with Democratic principles.

He's airing footage of Mr. Specter saying that the party switch "will allow me to be re-elected," followed by the damning voice-over, "Arlen Specter is running to save one job. His. Not yours."

And he's using pictures of his 80-year-old opponent looking weak and bald from chemotherapy during his second bout with cancer -- a brazen tactic that former Allegheny County Coroner Cyril Wecht called "truly reprehensible."

Dr. Wecht has a point, but the overall strategy has been working. Three polls last week showed Mr. Sestak in a statistical dead heat, and one showed him as just as likely as Mr. Specter to beat Mr. Toomey in the general election.

Mr. Specter also could be swamped by a wave of anti-incumbency that has sidelined several long-term elected officials, including 14-term West Virginia Rep. Alan Mollohan.

At least one of Mr. Specter's stalwarts has deserted him this time around, as well. NARAL Pro-Choice America endorsed Mr. Sestak, whose votes are more in line with its agenda.

This was a marked change from the 1992 general election, when many women were furious with Mr. Specter's treatment of Anita Hill during the Senate confirmation hearings for Supreme Court Justice Clarence Thomas. Democrat Lynn Yeakel looked like a good alternative, but NARAL counted Mr. Specter as an ally and stayed out of the race. Now the group says the senator's "mixed record" of the past 15 years isn't good enough.

The end result will depend on turnout. As Post-Gazette political editor Jim O'Toole reported Friday, Mr. Specter is an old hand at getting out the vote, and the Democratic machine and the state's labor unions are throwing all their resources behind him. If Mr. Sestak is going to oust the five-term senator, he will have to match or exceed those efforts.

This is the kind of bruising primary Mr. Specter thought he'd avoid by switching parties. Now it turns out that the Democrats may not want him any more than the Republicans did. Ouch.

First Published: May 16, 2010, 4:00 a.m.