How will the battle over the Employee Free Choice Act affect Sen. Arlen Specter's complicated quest to be elected to a sixth term?

A month or so after enraging conservatives by his vote for President Barack Obama's economic stimulus package, the Pennsylvania Republican is in the crosshairs again over another huge test of Mr. Obama's clout: the Employee Free Choice Act.

Last week, the blogosphere was alive with speculation about an alleged "deal" between the senator and the AFL-CIO in which Mr. Specter, in exchange for supporting the act, would receive labor's full backing in next year's race.

"This is big," crowed Greg Sargent on The Plum Line, a Washington, D.C., politics blog. "Senior officials with the powerful AFL-CIO have privately assured GOP Senator Arlen Specter that they'll throw their full support behind him in the 2010 Senate race if he votes for the Employee Free Choice Act, a senior labor strategist working closely with the AFL on the issue tells me."

Of course, Bill George, president of the Pennsylvania AFL-CIO was saying just that more than a month ago -- publicly, not privately.

Not only that, Mr. George said, a "yes" vote on the act would prompt organized labor to actively register its members as Republicans to help Mr. Specter in the GOP primary.

"We put our money where our mouth is," Mr. George said.

At any rate, Mr. Specter may end up supplying the critical vote if the bill comes up as expected in May or June.

In 2007, when a similar bill was before the Senate, Mr. Specter was the sole Republican voting with Democrats for cloture to overcome a filibuster, a move that failed to attract the 60 needed votes. In a recent interview, however, Mr. Specter noted that his vote for cloture didn't mean he was supporting the bill, only expressing a desire to advance it so that labor law reform could be seriously considered.

The National Labor Relations Board is the real problem, Mr. Specter has stated repeatedly in interviews, hearings and in a 2008 law review article: dysfunctional and politicized, favoring business when the Republicans are in control and labor when the Democrats are, with some cases taking as long as 11 years to resolve.

Plus, he noted that his vote for cloture vote took place when there were 49 Republicans in the Senate, 49 Democrats and two Independents voting with the Democrats. A Republican president had vowed to veto the bill. Times have changed, he said.

For the time being, Mr. Specter is in full listening mode.

"Labor continues to press its case on the basis of a lot of jobs being exported, the pensions have gone to hell, lots of problems. And, as I say in my floor statement and law review article, I am well aware of the tradition of secret ballot on political elections and the difficulties of binding arbitration on the conducting of a business so I'm hearing people on all sides," he said.

Mr. Specter has two hurdles to overcome.

First there's next year's GOP primary, and he's expected to have a harder time than in previous years because so many moderate Republicans in the state have switched to the Democratic Party, a trend that began in the 1990s and accelerated in 2008.

According to recent data compiled by Roll Call, a Capitol Hill Web site, Republican registrations in Mr. Specter's suburban Philadelphia base -- Philadelphia and the four so-called "collar counties" encircling the city -- have dropped by 83,412. That's a number much larger than Mr. Specter's margin of victory -- 17,000 votes -- over then-U.S. Rep. Patrick Toomey in the 2004 primary.

With a more conservative GOP electorate, a vote against the act would give the moderate Mr. Specter a much-needed boost with the pro-business wing of the Republican base, while a vote for the act would go over like a lead balloon.

"Based on my conversations with our members, I can state the business community reaction to a vote by Sen. Specter for card check, including of course a vote for cloture, would be extremely negative," said Gene Barr, vice president of Government and Public Affairs for the Pennsylvania Chamber of Business and Industry, which nonetheless does not get involved in national elections.

If Mr. Specter votes against the act, "It will go a long way in helping him to control some of the damage inflicted when he voted for the stimulus package," said Charles Gerow, a Harrisburg-based Republican strategist.

Mr. Gerow argues that Mr. Specter can win the general election without organized labor's support, given his status as an incumbent, his fundraising and -- as a moderate -- his crossover appeal to Democrats.

Union representatives are equally confident they'll keep Mr. Specter on board.

"There's no one better than Arlen Specter at threading the needle of electoral politics," said Bill Samuel, director of government affairs for the AFL-CIO.

"This is a man who has stood up for the rights of workers to bargain collectively," he said. "Mr. Specter is extremely thoughtful and his diagnosis of the problem is fairly similar to ours. He acknowledges that the system is broken and that workers have lost their ability to bargain effectively, and I think we're going to reach agreement on how to fix it."

Still, it's important to remember that 2010's primary and general elections are still a year or more away -- and a lot can happen in a year.

Indeed, Jerry Gorski, head of the Associated Builders and Contractors Association, and owner of an engineering firm in Montgomery County, acknowledged as much.

While he is strongly opposed to the bill, "I am not going to make up my mind on whether to vote for Mr. Specter only on this one issue," he said.