At this point, both parties know they have too much to lose politically if the US goes into default. The President ultimately will be held responsible for the economy, along with members of his party. As for the Republicans, a critical mass understands that independents will not consider them responsible enough to be entrusted with a majority (or even possibly the presidency) next year if they continue to make demands that they know will not (or cannot) be met by the Democrats as they presently constituted, and which therefore involve playing a game of high-stakes brinksmanship with the already-faltering economy.
Look, the country is tired and afraid as the economy continues to deteriorate. The last thing Americans need is another financial panic. And they will be angry -- rightly so -- with any politicians who embroil our country in more unneeded drama in the cause of ends which, however absolutely good and right, are unattainable with a left-liberal Senate majority and the most left-wing president of most of our lifetimes.