There’s been a twist in the tax debate in the Senate. Before now, everyone assumed that the procedural votes today on competing tax plans were largely procedural, and would both get beaten back by forcing a 60-vote cloture threshold on them. But Mitch McConnell just announced that he would allow a majority vote on both proposals.

“Republicans will allow a simple majority vote on the two proposals,” McConnell said on the Senate floor. “By setting these votes at a 50-vote threshold, nobody on the other side can hide behind a procedural vote while leaving their views on the actual bill itself a mystery to the people who sent them here.”

The Democratic bill would extend the Bush tax cuts up to the first $250,000 in income and let the rest expire. The Democrats’ bill would also extend a series of middle-class tax cuts from the stimulus package and increase the capital gains and dividend rates. The Republican bill would merely extend all the Bush tax cuts for a year.

This calls into question who has the votes to pass the plan and who doesn’t. With Joe Manchin’s agreement on the Democratic tax plan, the working assumption was that Harry Reid had enough votes to earn a simple majority, and one of his talking points was that Republicans wouldn’t allow that. Now he has to hope he can get that simple majority, and that Republicans cannot. Joe Lieberman and Jim Webb have already said they’ll vote against the Democratic plan, and Democrats like Jon Tester and Claire McCaskill (both in difficult re-election fights) and Ben Nelson are wild-cards. Vice President Joe Biden is scheduled to speak at the fire fighter’s union convention in Philadelphia today at 1pm ET, so Reid may have to hold up the vote if he needs Biden to break a tie. A tie is unlikely if everyone votes, however, because Republican Mark Kirk continues to recuperate from a stroke.

There’s also the possibility that BOTH tax plans pass, at which point I have no idea.

None of this brings us any closer to getting a resolution on the tax issue. Even if Republicans were to sneak through their tax plan, and the House followed suit next week, the President will veto. So nothing’s likely to come of this. But it changes the expectations for today’s Senate votes.

One final note – I suppose this means that obstructionism isn’t sustainable when the spotlight is on.