Yesterday, the U.S. House passed what would be the first federal shield law to protect journalists’ sources. The voice vote wasn’t a surprise; the House passed the Free Flow of Information Act last year 398-21.

But the Senate is where things get interesting — and Minnesota’s vacant Senate seat could come into play.

Last summer, Republicans successfully filibustered the legislation, which gives journalists and sources qualified protection in federal court, something they enjoy in every state court except Wyoming. In 2008, a party-line 51-43 vote fell nine votes short of cutting off debate.

Dave Aeikens, a St. Cloud Times reporter who’s president of the national Society for Professional Journalists, says the failure wasn’t on the merits, but pre-election politics. “The Republicans were voting everything down — it involved oil-drilling politics, and they wouldn’t let anything on the floor that didn’t involve domestic drilling.”

So will the law triumph this year? Laurie Babinski, a D.C. attorney who’s working with the National Newspaper Association, calls it a “whole new ballgame” — but some old demons lurk.

Because the Bush administration opposed the bill last year (are you shocked?), pro-shield law forces had to get 67 votes even if they overcame the filibuster. This year, she notes, President Obama supports the bill, which knocks the number of Senators needed back to 60 (if there’s a filibuster) or 51 (if not).

With the Democrats surging to 58 seats after the ’08 election, a majority is all but certain. But a filibuster-proof majority? Well, that’s where Minnesota’s vacant seat may come into play.

Pennsylvania Republican Arlen Specter is sponsoring the Senate bill and fellow Republican Dick Lugar is a co-sponsor; if all 58 Democrats hold together, that’s 60 votes. But if anyone defects, Coleman or Franken could be the 60th.

Importantly, it doesn’t matter who wins the seat, just that someone does. Aeikens says Norm Coleman is on record supporting a federal shield law, even though he voted to uphold the filibuster last year. Al Franken is also a supporter.

Barring Texas Sen. John Cornyn’s hope for a years-long Minnesota stalemate, it’s possible Al or Norm will get to Washington before a shield vote.

Babinski notes “things are not moving anywhere as quickly” in the Senate, as journalists and senators haggle over thorny shield-law exemptions. The House bill compels sources to be divulged in limited national-security circumstances; House GOP dissidents complained the exemption is too narrow. (This might be one circumstance where supporters defect, or backers such as Coleman shape the bill’s ultimate scope. Democrats and the new Commander in Chief may also support some adjustments.)

The Senate bill, meanwhile, does not allow journalists to claim privilege for outtakes or other things “left on the cutting room floor,” Babinski notes. Overall, though, she is “fairly confident” there will be enough votes to pass something.

For more on the legislation, see reports here, here and here. The House GOP caucus has a well-balanced summary here.