U.S. Sen. Arlen Specter's vote for the Senate stimulus bill is stimulating long-festering Republican opposition to his re-election.

Mr. Specter, whose term expires next year, was one of three GOP senators who voted for the Senate version of the economic recovery measure. The vote prompted Glen Meakem, the CEO of the former Internet firm FreeMarkets, to declare his determination to play a still unspecified role in ousting the veteran Republican in the 2010 GOP primary.

"There will be a Republican primary fight for Specter's Senate seat in 2010," the entrepreneur and conservative talk show host said in a statement, "and I am going to be actively involved in electing someone who will do what's right for Pennsylvania taxpayers, not the Washington lobbyists."

While his release notes that Mr. Meakem "is often mentioned as a candidate for statewide office," the businessman said in a subsequent interview that he hasn't made up his mind on whether he or someone else should carry the conservative standard against Mr. Specter.

Another possibility is Peg Luksik, a conservative activist and former candidate for governor who said yesterday that she is considering a bid for the Specter seat.

"I'm thinking about it," said Mrs. Luksik, who was the campaign manager for Republican William Russell's unsuccessful challenge to Rep. John P. Murtha last year. "Right now, the family and I are talking. ... I really think that it's important. It's time for somebody to tell folks in Washington that enough's enough."

Mr. Specter, the longest-serving senator in the state's history, barely survived a 2004 primary challenge from former U.S. Rep. Pat Toomey before winning easily in the general election. Many Pennsylvania conservatives had hoped to see a re-run of that race next year, but Mr. Toomey, the president of the Club for Growth, signaled recently that he is more interested in a run for governor.

Mr. Specter, a liberal on social issues such as abortion rights and stem cell research, has often faced conservative opposition while managing to win five terms in the Senate. He has already declared his candidacy to run for re-election next year and has raised roughly $5 million as a down payment on that effort. The former Philadelphia prosecutor faced his toughest intra-party test in 2004 when Mr. Toomey defied much of the state and national GOP hierarchy, only to lose in a primary by just about 17,000 votes out of more than a million cast.

Mr. Specter acknowledged the unpopularity of his vote on the stimulus package and its implications for his political future in a news conference earlier this week.

"I believe that my duty is to follow my conscience and vote what I think is in the best interest of the country. And the political risks will have to abide."

In an interview last night with MSNBC host Chris Matthews, Mr. Specter said of his vote for the Senate measure, "This is a very tough matter and we swallowed a big, bitter pill and we did this only because the economy is in such perilous shape."

Despite that closely watched vote, the Republican appeared to leave a door at least slightly ajar to a break with the Obama administration in the event that a conference committee produces a final compromise measure that strays too far from the Senate language he agreed to along with Sens. Olympia Snowe and Susan Collins and the chamber's Democrats.

"When we worked this through, we went as far as we could. ... But if somebody wants to restructure the arrangement, they may end up with no arrangement at all," he said in the MSNBC interview.

One factor that could make Mr. Specter more vulnerable to a conservative candidate next year is the fact that the state Republican party has lost hundreds of thousand of registered voters to the Democrats over the two election cycles since his last primary victory. Many of them were the kinds of liberal and moderate Republicans who have traditionally been among Mr. Specter's core supporters. Balanced against that are the long-standing associations and name recognition he's cultivated during his record tenure.

A conservative challenge to the veteran lawmaker would be welcome to Democratic tacticians for several reasons -- for the financial drain it would pose to the well-funded incumbent, for its potential to divide the GOP and for the possibility that it would produce a nominee that they could portray as out of the mainstream of state politics.

So far, Joseph M. Torsella, the former CEO of the National Constitution Center in Philadelphia, is the only Democratic candidate who's officially declared his interest in the race. Other Democrats mentioned as possible contenders include U.S. Reps. Allyson Schwartz, and Patrick Murphy, who represent districts in the Philadelphia region; state Rep. Josh Shapiro of Montgomery County; and state Auditor General Jack Wagner, who is also weighing a bid for governor.