The Atlantic’s Megan McArdle:

…Our AAA is not at risk because our current fiscal path is unsustainable, but because ratings agencies know what many GOP freshman and party activists apparently do not: that doing the unpopular things required to get the budget in balance is going to require both parties to hold hands and jump together. Otherwise, whoever forces through their unpopular plan (huge tax increases/massive spending cuts) is going to get trounced at the next elections by an opposition party promising to undo whatever it is the party in charge has just done.

My reading of what the ratings agencies have said is that if the GOP somehow manages to force the Democrats to do everything their way, this will not secure our AAA; it will guarantee that we lose it, because it will show that we are currently unable to make the ugly bipartisan compromises that long-term budget balance requires, and raises the risk that sometime in the not-very-distant future, the other party will retaliate by threatening default.