Still, I think the main asymmetry here lies in the nature of the demands of the two sides -- Democrats insist on both revenue and spending cuts, Republicans on just spending cuts -- rather than their willingness to compromise the demands themselves. Jonathan Bernstein writes:
It's absolutely true, as Greg says, that Harry Reid and other Democrats talk about how much they want to reach a deal and how flexible they intend to be, while Republicans have been spending the last week groveling to Grover Norquist and Rush Limbaugh. My guess is that it's easy to overstate how important that rhetoric is. Basically, at this point both sides are attempting to appeal to the constituencies they care about not in terms of substantive policy, but in terms of their attitude towards politics. But those constituencies also do have substantive concerns, and I'd expect those to trump attitudes about process down the line (although expect public statements to remain framed by those process concerns). In other words, it makes perfect sense that Democrats express eagerness to make a deal now, and then after there's no deal they will express their frustration that Republicans weren't willing to meet them halfway. But that doesn't mean that Democrats will in fact be any less vigilant in fighting for their preferences than the Republicans will be in fighting for theirs.
I think the main thing to understand here is that the supercommittee just does not need to strike a bargain. The automatic cuts that will occur if Congress doesn't cut the deficit are designed to threaten both parties. But, rather than force the parties to make a deal to cut the deficit, it could just as easily force the parties to make a deal to cancel out the cuts after they fail to make a deal. Remember, the cuts don't take effect until 2013. i don't see how that threat could force Democrats to accept cuts to entitlement programs without higher revenue.