As the Senate prepares to vote today over whether to close debate on legislation granting the District a voting seat in the House of Representatives, no one can safely say whether the votes will be there to head off a threatened filibuster. Senate Minority Leader Mitch McConnell (R-Ky.) made his opposition to the bill painfully clear in a floor speech yesterday, and voting rights activists have been scrambling to gain enough Republican allies to reach the 60-vote threshold. This morning brings news that the task may have become harder due to Sen. Robert Byrd (D-W.Va.).

According to FreeRide, Byrd, the Senate’s longest-serving member, announced that he opposes the bill, arguing in a statement:

I oppose S. 1257, because I doubt that our Nation’s Founding Fathers ever intended that the Congress should be able to change the text of the Constitution by passing a simple bill. The ability to amend the Constitution in only two ways was provided with particularity in Article V of the Constitution for a reason. If we wish to grant representatives of the citizens of the District of Columbia full voting rights, let us do so, once again, the proper way: by passing a resolution to amend the Constitution consistent with its own terms.

But Sen. Byrd’s office announced this morning that he would miss the vote, choosing instead to attend an honorary doctorate ceremony from Wheeling Jesuit University on behalf of his late wife.

There are a number of ways to see this. Byrd may really oppose the bill, but may also be sympathetic enough to the goal to want to avoid casting a vote against it. Conversely, Byrd really does have something else to do, and his opposition of the bill isn’t strong enough to make him want to change his schedule.

Either way, with Byrd’s absence, the Senate (if all other members attend) is left with 49 Democrats, 49 Republicans and 1 Independent. Sen. Joseph Lieberman (I-Conn.), the sole Independent, has long been a supporter of the legislation, giving it a surefire 50 votes. On the Republican side, some five senators are committed supporters, though three others, including Sen. Arlen Specter (R-Pa.), Sen. Sam Brownback (R-Kan.) and Sen. Richard Lugar (R-Ind.), have expressed sympathies but not committed to a vote up or down. The outcome will likely boil down to how hard Sen. McConnell lobbies his caucus; how actively Sen. Orrin Hatch (R-Ut.) lobbies against McConnell and pulls Republicans to vote for the bill; and the impact the influence of Sen. Byrd’s statement might have on wavering members.

Whichever way things go, the debate is likely to be spirited. Things kick off at 2:15 p.m., and we’ll be live-blogging the whole thing.