The centrist fantasy of a Grand Bargain on the budget never had a chance. Even if some kind of bargain had supposedly been reached, key players would soon have reneged on the deal — probably the next time a Republican occupied the White House.
For the reality is that our two major political parties are engaged in a fierce struggle over the future shape of American society. Democrats want to preserve the legacy of the New Deal and the Great Society — Social Security, Medicare and Medicaid — and add to them what every other advanced country has: a more or less universal guarantee of essential health care. Republicans want to roll all of that back, making room for drastically lower taxes on the wealthy.