There are at least two sticking points. Obama has insisted that the first new revenues come from raising tax rates on couples who earn above $250,000; Boehner has insisted that, no, they should come from limiting personal deductions and closing loopholes. Democrats like Sen. Harry Reid say the deduction/loophole route won’t yield enough revenue. The Washington Post editorial page argues that in fact, limiting deductions to $50,000 per taxpayer would raise about $750 billion over 10 years, nearly matching the $800 billion that would be raised through the proposed tax hikes on the top 2%.

In Washington of yore, when leaders sat down and negotiated face to face, those differences would seem highly bridgeable. Get part of the revenue by raising rates slightly (not all the way), and get the rest through deductions/loopholes. Both sides get some of what they want. …

In short, we have known the framework of a grand bargain for a long time, and in theory, we should be closer to it than ever. But this week, there is a palpable sense in Washington that the parties are drifting apart and chances of an agreement before Christmas are diminishing. Erskine Bowles, a former White House chief of staff and former co-chairman of Obama’s debt commission, now puts the chances of a deal that prevents us from going over the fiscal cliff at only one in three.