Both sides are very vague on where their portion is coming from. Neither side plans to give anything up. The concept of centrism and compromise has been completely lost.
Just for fun, from Intrade:
The US debt limit to be raised before midnight ET 31 Dec 2012
Last prediction was: $3.36 / share
Today's Change: -$2.00 (-37.3%)
Looks like fewer and fewer people think we'll find a solution. Our politicians are really letting us down.