Joe Klein, a veteran of the New Yorker, Newsweek and Time, is the author of seven books, including “Primary Colors.”

I am trying to remember the person I was in 1968. I was 22 years old and a recent college graduate. I was angry, infuriated by the war in Vietnam and racial segregation. It was my first chance to vote in a presidential election. I was living in New Jersey — very briefly — and I voted for Dick Gregory, the brilliant comedian running as a write-in candidate, instead of Hubert Humphrey, the Democrat running against Republican Richard Nixon. It was a protest vote, obviously. I regret it to this day.

Humphrey barely lost New Jersey to Nixon. Gregory’s 8,084 votes would not have turned the state. But I wonder: What would have happened if I, and hundreds of thousands like me nationwide, had given Humphrey the same level of energy, support and enthusiasm we lavished upon Eugene McCarthy and Robert F. Kennedy in the primaries?

Humphrey was the Joe Biden of his day, a standard-issue establishment Democrat. He was known to be a lovely man who had a problem with his mouth: He talked too much. He had started out as a civil-rights crusader in Minnesota, but that seemed like ancient history to me. Worse, he was Lyndon B. Johnson’s vice president and a supporter of the war in Vietnam until late in the campaign. We — the Bernie Bros of the moment — had driven Johnson from the race. It was infuriating that we’d done so in order to make the world safe for Hubert Horatio Humphrey.

In retrospect, my vote was an act of blind defiance. I was part of a generational movement — not just political but also cultural, perhaps more so. We were so different from our parents: Our music was different, we dressed differently — vehemently informal and provocative, we wore our hair long (letting our “freak flag fly,” in the words of a contemporary song). Our parents were so pathetic, especially when they started to imitate us by lengthening their sideburns and wearing, yuck, leisure suits.

We were counseled by our elders: Vote the lesser of two evils. But Humphrey’s kindness and humanity simply didn’t register. We saw only this wimpy, old guy who was probably lying about his newfound opposition to the war. And it didn’t really matter if Nixon won: We were young; we had a world to win, an establishment to overthrow. We had a plenty of time. Four years of Nixon would bring the country to its senses. What was one election?

It was more than 20,000 American deaths in Vietnam and uncountable numbers of Vietnamese people killed and wounded. It was the onset of a politics — Nixon’s Southern strategy — that began the process, which continues to this day, of white racial backlash. It was a descent, by many of us, into a reflexive, silly left-liberalism that caused the Democratic Party to suffer more than 20 years of defeat before being hauled back to reality by Bill Clinton in 1992.

In 2016, I asked Hillary Clinton if the 1968 version of herself — the antiwar civil-rights crusader — would have voted for Bernie Sanders or Hillary Clinton in the New Hampshire primary. She made a brave attempt to argue against a vote for Bernie, but we both knew the real answer.

We also knew what the 1968 versions of ourselves had learned in the 50 intervening years. We had learned the importance of stability, especially in a democracy. In Beirut in 1978, I had seen a sophisticated city ripped to shreds by tribalism … and had learned how fragile a civilized society can be. We had both learned how hard it is to make a difference, that the best change comes incrementally and only with a national consensus. We had both learned that idealism needs to be enhanced by civility and some institutional memory.

I am not trying to persuade young Sanders zealots that they should cast a vote for this year’s version of Humphrey. Not yet. In any case, they’re not going to listen to a geezer like me. I understand their impatience and anger, even if I don’t understand why a 78-year-old man insists on the puerile offensiveness of calling himself a “socialist” when the countries he purportedly admires — the Scandinavians — are bastions of free enterprise tempered by a robust welfare state. Perhaps Sanders needs to grow up a little, too.

My question to young voters is this: If Sanders loses the nomination to Biden, will you be as stupid as I was in 1968? Will you allow the country — the federal government, the Environmental Protection Agency, the judiciary, the diplomatic corps — another four years of President Trump? Are you entirely sure we can survive that?

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