According to two as-yet unconfirmed reports, centrist Sen. Arlen Specter (R-Pa.) will oppose the Employee Free Choice Act (EFCA, a.k.a "card check"), as well as the procedural motion to bring it to a vote in the Senate.

Washington Independent's David Weigel suggested in a tweet Tuesday afternoon that Specter will oppose cloture on EFCA, while the Drudge-esque reported, citing "multiple sources," that Specter will oppose cloture and the passage of the bill itself.

Specter is expected to make a statement on the Senate floor about his position sometime this afternoon.

Unions have been courting the centrist Republican, promising to fully back his tough reelection bid in 2010 in exchange for his support of the card check legislation. The bill is teetering on the brink of a filibuster-proof majority, but will need the support of all Democrats and some centrist Republicans to secure passage.

Specter's position has also been a key issue in his likely primary race against Club for Growth Chairman Pat Toomey.