But just as in 2016, when Bernie Sanders specifically said he did not want to talk about Hillary Clinton’s emails, Sanders again ruled out making completely fair-game criticisms of his opponents’ ethical lapses. Sanders is just interested in his revolution and ideology, not in actually disqualifying the opponents who represent the system he would radically alter.

And even if you like Joe Biden, you have to wonder if Sanders has done a disservice to the eventual nominee. Part of the reason to hold a primary is to see whether the candidates can withstand tough scrutiny, whether they can answer the expected charges made against them. Sanders never did this for Clinton, and he hasn’t done it for Biden. He is like the sparring partner who fails to test the prizefighter’s weaknesses in the training camp before the big match. Donald Trump will not hold back on potential ethical issues. Because Bernie Sanders never did what was required to win, Democrats now go into a consequential general election not knowing if Joe Biden has a glass jaw.