By refusing to embrace Simpson-Bowles as the basis of a Grand Bargain, and instead offering a watered-down version, Obama has left a gap for a sane Republican or independent candidate. Why was Christie popular among G.O.P. moderates and independents? Because he seemed ready to tell hard truths that Obama has started to shrink from. Had Christie — a moderate on gun control, climate change and immigration who has also backed Simpson-Bowles — run and won significant support, he would have forced Obama back to the center.

Then, instead of a race between the Democratic left and the Republican right — in which the whole country would lose because the winner would not have had a mandate for the real change we need — we would have had a race between the Democratic center, independents and the Republican center. Then the whole country would win. Because whoever captured the presidency would have a mandate to actually implement some version of the Grand Bargain needed to get growth going again — and growth is the only sustainable cure for unemployment, the deficit and inequality.