But Biden’s personal fortunes are not the only thing tanking. Throughout the evening it was clear that he was being attacked not simply because he is the front-runner but because the Obama-era moderate liberal consensus he represents is not acceptable to any segment of the Democratic base. To earnest progressives, his steadfast opposition to single-payer health care and his wait-and-see approach to climate change are unacceptable; to neoliberal moderates who might agree with him about all of the former, his rhetoric on race and his confrontational attitude toward issues such as abortion are disqualifying. Even Bennet spoke cryptically of “the divisive politics of the last 10 years.”

This put Biden in a difficult position. It seems never to have occurred to him that Obama remains a popular figure among the Democratic base despite rather than because of his actual record in office. You cannot premise your entire campaign on the idea that you are Obama’s closest political confidante and then insist that any of the administration’s failings — on immigration for example — have nothing to do with you. Obama’s seeming refusal to endorse his former vice president has never looked wiser.