Dear Comrade Sanders:I’m not being sardonic. Your talk of socialism has been the best part of your campaign, even if you have been less than skillful at drawing the line between your own democratic left and its antidemocratic cousins. You have pointed out that society is more than a collection of individuals, which is socialism’s ultimate instruction, and you have railed against the inequalities, which is the penultimate instruction; and you have gotten everyone’s attention. Your appreciation of socialism’s history in America ought to alert you to something, though.A century ago, when your hero Eugene V. Debs was the Socialist Party’s perennial presidential candidate, a good many people supported him and the Socialist Party as a whole because they wanted big social reforms on behalf of the American working class, and they wanted those reforms to conform to the latest word in social science. Neither the Republicans nor the Democrats in those days were offering much along those lines. And so, people voted Socialist because politically they were homeless. Then times changed. Circa 1933 the Democrats began to entertain a modernizing impulse. And the Socialists were left with a decision to make: to remain immured in their own tiny political party? Or to take their place within the vast Democratic Party? A small Socialist minority decided to preserve the old party.Everyone else joined the Democrats, in one way or another. And now came American Socialism’s greatest achievements. The Socialists-who-joined-the-Democrats proved to be a main engine of the Franklin Roosevelt reforms in the 1930s and ’40s. The unions that had come out of the Socialist movement became central players in the Democratic Party. No one among those old-time Socialists mistook the Democratic Party in those days for perfection on earth. But everyone understood that, even so, the Democrats, strengthened by an infusion from the left, had become, at last, what the old-time Socialists had always wanted to create, which was a party of big ideas and practical reforms—the party of the New Deal, which became the party of the Fair Deal, and of civil rights, and of the Great Society, and of Obamacare, which adds up to some 80 years of social progress.Comrade Sanders, it is not true that Hillary is the lesser of two evils. Hillary is the Democratic Party’s reform tradition incarnate. She is, after President Obama, the great hero of socially responsible healthcare in America. Many years ago, the Socialist Party was the party of the social-policy wonks, who came up with reform proposals and knew how to describe them lyrically. Today the reform wonks are Democrats, and Hillary is their candidate. To speak lyrically is not within her power, though. Bernie, has it occurred to you that you might help? Hillary has the detailed proposals, but not the poetry; and you have the poetry, but not the detailed proposals. You and Hillary, then—why not join forces?At the start of your campaign, it was easy to imagine that someday soon you might, in fact, join forces with Hillary—if not instantly, then soon enough. “The American people are sick and tired of hearing about your damn emails” was one of your finest lines, and it appeared to signal an impending alliance. Campaigning has gone to your head, though. Now you are the anti-Hillary candidate, and you seem intent on wreaking whatever damage you can. Perhaps you have talked yourself into supposing that, if you threw in the towel, as everyone but your own narrow following and the Republican Party wants you to do, your withdrawal would signal a defeat for your cause and your ideals. But why should you believe this?Hillary has told us that privately she communes with the ghost of Eleanor Roosevelt, who offers sage Democratic advice. Bernie, you need to commune with the ghost of David Dubinsky of the International Ladies Garment Workers Union, whom you must remember from childhood. Dubinsky’s ghost could remind you that Socialism’s victories in 20th-century America mostly came about after the old-timers like himself had sloughed off their left-wing sectarianism and had made their way into the Democratic coalition. Maybe the ghost could clue you in on foreign affairs. On Israel the old-time American labor leaders from Socialist backgrounds tended to be solid: a matter of socialist internationalism. But mostly a proper left-wing ghost from those days ought to be able to lay out to you the necessity, from a progressive standpoint, of promoting the Democratic Party, instead of undermining it. To become Hillary’s most vigorous and stentorian working-class champion—yes, that is what an old-time left-wing ghost would advise you to do.The ghost would say: “The magnificent and frustrating Democratic Party needs the left-wing senator from Vermont to play this role— needs him to bring his own increasingly wrongheaded campaign to a merciful finish, and needs him to lend to Hillary what her own campaign sorely lacks, which is a working-class eloquence. The cause of social progress in America requires this now.”Think, Comrade.***To read more of Paul Berman’s essays and criticism for Tablet magazine, click here.