DeLong:

"But by my back-of-the-envelope count, the deal the Obama administration has agreed to still leaves a net fiscal impetus of -1.75% of GDP to hit the U.S. economy in 2013. "

Commenter Sadowski at EV:

"If it's delayed for two months and then goes into effect that brings it to 0.67% of GDP. Add in 0.56% for the payroll tax increase and 0.1% for high income tax increase (it's actually less) and you get to a negative fiscal impulse of at most 1.33% of GDP. That's less than 46% of the 2.9% negative effect on GDP estimated by the CBO, not 60%, as estimated by DeLong."

Bernstein:

As I write, the House hasn’t passed the bill yet, but if they do, as expected–with mostly D’s, btw–then we’re looking at some serious negative fiscal impulse coming…I’d guess around 1% of GDP (maybe less with no sequester).

Dean Baker:

We are now entering a new round of negotiations over extending the debt ceiling where the Republicans would appear to hold many of the cards.

While the consequences may not be as dire as the pundits claim, no one could think it would be a good idea to allow the debt ceiling to be reached and force the government into default. The Republicans intend to use this threat, however, to coerce further concessions from President Obama. The president insists that there will be no negotiations over the debt ceiling: no further concessions to protect the country's financial standing.

At this point, though, is there any reason for people to believe him?

This is a president who encouraged members of Congress to vote for the Troubled Asset Relief Program (Tarp) in 2008 with a promise that he would put bankruptcy cramdown for mortgage debt (allowing restructuring of housing loans for people with distressed mortgages) at the top of his agenda once he took office. This is a president whose top aids boasted about "hippie punching" when they ditched the public option in the Affordable Care Act. This is a president who has explicitly put cuts to social security on the agenda, while keeping taxes on Wall Street speculation off the agenda.

And this is a president who decided to put deficit reduction, rather than job creation, at the center of the national agenda – even though he knows the large deficits are entirely the result of the collapse of the economy. And, of course, he is the president who appointed former Senator Alan Simpson and Morgan Stanley director Erskine Bowles to head his deficit commission, enormously elevating the stature of these two foes of social security and Medicare.

Given his track record, there is little doubt that President Obama can be trusted to make further concessions, possibly involving social security and Medicare, in negotiations on the debt ceiling. Oh well, at least we can laugh at the experts being wrong about the fiscal cliff "Mayan apocalypse".

I think it's more of an open question.