cursory following suggest that the only blame to lay at Democratic feet is Obama and other leaders not having the balls to stick to their guns when compromise was so obviously not enough. Those revenue increases HAD to come through and didn't because no one fought for them.
I don't think that's quite right. Despite what S&P said about taxes the real problem they had wasn't long-term but short-term. Make no mistake, the US is being punished for the debt ceiling crisis, not being neutrally adjudged of our future creditworthiness. So much of the world's debt is invested in US dollars that until all that money can be disentangled it's almost meaningless to talk about our creditworthiness. We owe money in dollars, and we have the capability to print as many of them as we want. If we sink, China and the world sinks with us, which means as a practical matter that in the short to mid-term we're incapable of sinking. Unless someone on the inside sabotages the boat. We're being punished because it's structurally possible for Congress to cause the US to default, and they recently demonstrated that they were willing to take that risk. If the US had reached a deal a month ago that included zero revenue but increased the debt ceiling anyway, I'm confident we wouldn't have faced a downgrade.
Where I've heard Democrats are truly at fault, and this seems correct to me, is that they did not insist on raising the debt ceiling in exchange for allowing the Bush tax cuts to continue until 2012. Those tax cuts were set to expire in 2010, which means that Democrats had a structural advantage at that point in time - all they had to do was not agree to deal and the cuts would have expired automatically. This is the mirror of the advantage Republicans had in the debt ceiling debate. And political analysts contemporaneously were scratching their heads that Obama didn't demand a debt ceiling increase at the time. So you can blame Obama, and Democrats in general, for not driving a harder bargain last December when they were the ones with the upper hand. Let's hope they get this right next time the cuts are set to expire.
(Oh, but don't let that stop you from blaming the GOP first and foremost. Blaming Democrats for the downgrade is like blaming SWAT when hijackers shoot the hostages.)
EDIT: managed to make it through a whole argument without using a single one of the many and various bad words I used when I was talking about this in chat! Yay civility?