WASHINGTON -- 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.
That's why Vice-President Joe Biden and White House Interim Chief of Staff Pete Rouse invited House Democratic Leaders to the VP's mansion Saturday night for what turned out to be a two-hour meeting.
The existence of the meeting has been reported, but not the contents.
The topic, according to a source close to outgoing (but still in charge) House Speaker Nancy Pelosi, was how to cajole liberal Democrats in the lower chamber into accepting the results of the deal President Barack Obama and Senate Republicans are trying to cut.
The participants talked in detail of what elements should or should not be in a Senate package so that it can win the requisite vote in the House. And they discussed specific members and blocs -- what they would need (in the bill or elsewhere) to be supportive.
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.
But the real question is: What else, if anything, are rank-and-file Democrats going to require support with the deal?
That is an urgent, but not necessarily cataclysmic matter in the Senate. If Obama strikes a deal with the GOP, he and they will need only 18 out of 58 Democratic senators to go along with it to ensure that the coalition has 60 votes to prevent a deal-killing filibuster.
One Senate Democrat told me last night that he and his fellow liberals might try to stop the deal -- even if it means risking the possibility that all of the tax cuts are allowed to expire on December 31.
But that tough talk not withstanding, it seems a fairly idle threat. Even if GOP Leader Mitch McConnell loses a few of his fellow Republicans, Obama, Senate Democratic Leader Harry Reid and McConnell would still seem to have enough room to work with.
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.
And that is where the real crisis could kick in for White House, which increasingly is in the position of fighting with its party base.
The House arithmetic is dicey -- which is why Biden and Rouse spent two hours discussing it with Pelosi, Majority Leader Steny Hoyer and House campaign chairman Rep. Chris Van Hollen.
If all House 179 lame-duck-session Republicans support a two-year extension (by no means certain), Pelosi still would need to round up 39 Democratic votes for approval of the Senate version.
The assumption is that Democrats would not want to risk blowing up the deal -- let alone risk being held responsible for raising taxes on everyone in the midst of a lingering Great Recession.
But some Democratic backbenchers, increasingly estranged from the White House and the president, seem willing to do so -- or at least talk bravely about it. "I don't see why we don't try it, what the heck?" said one Democratic senator who nevertheless wasn't convinced enough of his position to risk attaching his name to it.
Ironically, it may be up to Pelosi -- seen my many as a liberal holdover who nevertheless ran for and won another term as Democratic leader -- to sell tax cuts for the rich to her fellow liberals in the House. They may not like her as much after that.
HuffPost Politics brings you the top political stories three days a week. Learn more