Biden decisively won tonight because all that mattered was whether or not he had a catastrophic stumble, and he didn’t, and whether or not he turned in a plausible performance, and he did. He was overly defensive and probably created lots of fodder for fact-checkers in the jousting over his record on entitlements, and he went even further left on immigration and fracking for reasons that are hard to fathom. But he won the beginning of the debate over the coronavirus and scored points on Bernie’s foolish call for a political revolution and on his reprehensible praise for Communist dictators. Biden is the presumptive nominee largely because he is the acceptable alternative to Bernie, and most Democrats will probably look at tonight and think he will be able to present himself as an acceptable alternative to Trump, too, in the fall.