Sanders’s remaining in the race should serve several salutary purposes for the party and the country. First, seeing him lose overwhelmingly week after week will dispel the notion that the Democratic Party has moved left, or that he is in a dominant position to negotiate with the overwhelming winner. It’s not clear why the Biden camp should “give” Sanders anything.

Second, it is good to keep Biden in fighting form, continuing to boost turnout and showing, as he did in Philadelphia, how presidential he is. Biden can pivot to the general election, essentially ignoring Sanders. (His planned speech on the coronavirus is the perfect opportunity to leave Sanders out of the discussion entirely.)....

Whoever is to replace Sanders as the standard-bearer for the left — hopefully someone as smart and wonky as Sen. Elizabeth Warren (D-Mass.) — will need to learn how to win elections. (Hint: It is not by scaring voters or attaching oneself to the socialist label.) When in office, a new generation of leaders on the left will need to learn the art of deal-making rather than waste years, as Sanders has, rabble-rousing but accomplishing nothing. Unlike Sanders, Warren (or whoever else takes the reins) will not be burdened by a record of reflexively praising dictators nor be driven to attack fellow Democrats.

Sanders will end the race at some point, a diminished figure. In retrospect, his wins in 2016 will be seen more as an anti-Hillary Clinton vote than a pro-Sanders vote. How he behaves at Sunday’s debate will determine whether he leaves a bad taste in the mouths of Democrats.