By Jon Keller

BOSTON (CBS) – Bernie Sanders’ biggest problem wasn’t the “corporate media,” the Democratic “establishment,” Barack Obama’s friendship with Joe Biden, Elizabeth Warren’s reluctance to endorse, or any other target of his many bitter grievances.

It was himself.

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The sight of Sanders, one of the most authentic and influential politicians of the past decade and the front runner in the Democratic race as recently as eleven days ago, headed once again for the also-ran bin after Tuesday night’s round of primaries (and one caucus), is the result of many factors. But foremost among them are Sanders’ familiar flaws.

In a campaign when Democrats have made it clear they prioritized ousting Donald Trump over all else, Sanders offered a tepid electability argument that got weaker as the race wore on.

If recent presidential elections have taught us anything, it’s that Democrats win easily when the black vote turns out, and lose when they don’t. Black voter support for Hillary Clinton in 2016 killed the Sanders campaign after its promising start in nearly-all-white Iowa and New Hampshire.

Sanders had three years since then to make himself competitive among black voters, and he couldn’t do it, despite promoting policies and rhetoric that in theory ought to have paved the way. It’s not some sort of white-guy-from-Vermont-can’t-connect-with-voters-of-color problem; Sanders has gathered impressive support from Latinos.

But from his ill-advised public musings about promoting a challenge to President Obama in 2012 right up through his avoidance of the Selma “Bloody Sunday” march commemoration, Sanders instead has seemed more inclined to pick a fight with the black establishment than to court it.

It was one thing when Sanders struggled to peel women away from Clinton in 2016. But his gender gap problem has persisted. Elizabeth Warren’s claim that he told her a woman couldn’t win in 2020 didn’t seem to help her much, but it surely reminded some women why they didn’t like Sanders.

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Any who ventured online and encountered the Sanders troll army didn’t need reminding.

And in that key moment after the February 22 Nevada caucuses when the party focused most intently on the prospect of Sanders as its nominee, what did Bernie do? Go on “60 Minutes” and take the bait, singing the praises of that glorious workers’ paradise, Fidel Castro’s Cuba.

When Pete Buttigieg glared at Sanders in the final pre-South Carolina debate and said “I am not looking forward to a scenario where it comes down to Donald Trump with his nostalgia for the social order of the 1950s and Bernie Sanders with the nostalgia for the revolutionary politics of the 1960s,” it was a devastating putdown, “OK Boomer” on steroids. It simultaneously deflated the pro-Sanders fervor of younger voters (who were already showing more interest in attending Sanders rallies than showing up to vote for him) and reminded older ones why the thought of Sanders as the nominee was so unappetizing.

Little if any appeal to blacks and women.

A tendency to cling to shards of outdated ideology.

Dubious electability.

And one more thing fueling Sanders’ now-certain defeat. From his New York Times endorsement interview:

“I’m not good at backslapping. I’m not good at pleasantries. If you have your birthday, I’m not going to call you up to congratulate you, so you’ll love me and you’ll write nice things about me. That’s not what I do. Never have. I take that as a little bit of a criticism, self-criticism. I have been amazed at how many people respond to, ‘Happy Birthday!’ ‘Oh Bernie, thanks so much for calling.’ It works. It’s just not my style.”

The simplest, most basic, easiest-to-execute form of ingratiation – the mother’s milk of politics – is “not what I do”?

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OK, Boomer. Then take a seat.

Jon Keller