Sen. Arlen Specter's decision to become a Democrat was supposed to be the easy path to reelection.
So much for that.
Specter's move ignited a firestorm in Pennsylvania and beyond. It's left him with new enemies in both parties, even though he has a set of powerful friends that includes President Obama and Vice President Joe Biden.
Rep. Joe Sestak, D-Pa., told ABC News that while he hasn't made up his mind, he's closer to seeking the Democratic Senate nomination than he was before the party switch, given the way the Democratic establishment has sought to rally behind Specter before Pennsylvania voters get a choice.
"How this was done gives me grave concerns. That's not the ideal that we came to Washington for," Sestak said.
"I really was taken [aback] by the Democratic political Washington establishment saying, here's your candidate, Pennsylvania," he added. "I thought, when I came here, and when President Obama came here, we weren't for an establishment -- we're for change."
Specter, 79, now faces the real possibility of both strong primary and general-election battles.
While Sestak and others weigh primary candidacies, former governor Tom Ridge, R-Pa., is being courted by state and national Republicans to carry the GOP banner. Already, former Rep. Pat Toomey, R-Pa., -- who almost beat Specter in the 2004 Republican primary -- is in the race, and raising money at an impressive clip.
Sestak said he will be closely monitoring Specter's statements and votes over the coming months, to make sure he's helping the country move forward on areas including healthcare expansions and national defense.
"Arlen has a lot of questions to answer. If they aren't answered appropriately, I do believe we should have someone else carrying the banner for the Democratic Party, and for all Pennsylvanians," he said.
White House Press Secretary Robert Gibbs on Tuesday reiterated the president's support for Specter, even if Sestak or others challenge him in a primary.
"I think the president was pretty clear on this. Senator Specter has his full support and he'll do what -- what's necessary to see him re-elected," Gibbs said.
Sestak or another primary challenger can expect the help of liberal activists, many of whom have been waiting years or decades to defeat Specter.
In addition, rifts are appearing inside the Democratic Party that could cost Specter the support of organized labor, despite the Democratic establishment's promise to rally behind its newest member.
Top officials of the two largest national unions told ABC News Monday that they are unlikely to support Specter as long as he opposes their top legislative priority, the pro-unionizing bill called the Employee Free Choice Act.
"If a candidate isn't good for workers, we won't be there. If they are good for workers, we will be there regardless of their party," Richard Trumka, the secretary-treasurer of the AFL-CIO, said on ABCNews.com's "Top Line." "I mean, we supported Arlen Specter -- and he was a Republican -- because he was good for what was happening. He was good for our members at that time."
Andy Stern, president of the Service Employees International Union, met with Sestak Monday in Washington and conveyed to him the importance his members are placing on the Employee Free Choice Act.