The fly in the ointment of this tax cut deal appears to be in the House of Representatives, though I’m going to question the math here:

While the public focus of the Great Tax Battle remains riveted on the U.S. Senate, top Democratic insiders are privately worried about the real lame-duck end game: a last-minute, potentially deal-breaking revolt by Democrats in the House [...]

The Senate-based deal is likely to include a two-year extension of Bush-era income tax cuts, even for the wealthiest families and a reauthorization of the existing program of jobless benefits so that some 2 million Americans don’t lose them at Christmas [...]

The biggest problem — most seem to have forgotten — is in the House. Many seem to have forgotten that it is the House, which must originate tax bills, that last week voted by a 234-188 margin to limit the extension of the Bush tax cuts to families making less than $250,000 — Obama’s original campaign pledge.

Speaker-to-Be John Boehner denounced the vote as grandstanding “chicken crap,” but, being the legislative veteran that he is, he understood its procedural significance: It meant that whatever the Senate produces must come back to the House for another vote.

The vote would have to cross the House anyway, Mr. Fineman. And I’m not convinced that the House is a huge obstacle. On the vote on the rule, 33 Democrats sided with the Republicans. In that case, they were both blocking the tax cuts on the first $250,000 to come up for a vote. But they could be expected to side with the GOP on a tax cut deal, too.

I think the bigger problem would come from intransigent Republicans who don’t want to extend unemployment for another year. If you just get a non-trivial number opposing the bill from the right – 20-25 dead-enders – it makes it that much harder to find enough support on the left to get the bill passed.

And ultimately, I see this as less of a problem in the House than in the Senate, mainly because of the difference between a simple majority and a filibuster-proof supermajority. I could easily see Jim DeMint, Tom Coburn, Jim Bunning, and the right of the right opposing the deal on these grounds. That would raise the bar significantly on Harry Reid to round up the votes for passage.

I could see the kind of left-right alliance coming together – for very different reasons – to oppose the ultimate deal. And with 60 votes needed in the Senate, maybe the center will not be able to hold.