As the debacle of the last debate taunts the mind and haunts the soul of former New York City Mayor Mike Bloomberg, he should shelve the briefing books in favor of playing over and over again one classic movie series.

To survive the shifting terrain of a Democratic nomination minefield he needs to show more Rocky Balboa -- more grit, more fight and less contrition.

Rocky’s advice to Mike, as to the rest of mankind, is simple and sure: “It ain’t how hard you hit; it’s about how hard you can get hit, and keep moving forward. How much you can take, and keep moving forward.”

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If the Democrats want to take out a champion fighter on the other side of the fence, they need a fighter of their own. It fits the times as populists are on the rise and pragmatists are on the run; the Michael Bennets, Steve Bullocks and Cory Bookers give way to the Bernie Sanderses and Elizabeth Warrens.

This one development is not only shaping this presidential race but also elections across the earth where restlessness gives way to calls for reform and institutions yield ground to the vagaries of the popular will.

For Democrats, this is where history is both a guide and a warning.

John Kennedy was a charismatic visionary. LBJ was pugnacious in private but tame in public. Jimmy Carter was the plain-speaking moralist giving the country a therapeutic lift after Watergate; Obama gave the nation a historic lift by breaking a barrier.

The rest – the boring Al Gore, muddling Walter Mondale, the dour Mike Dukakis, and a lecturing Hillary Clinton – could be grouped together as uninspiring, unimaginative and flat. Not a fighter among them; not one Rocky Balboa ready to risk it all by going for it all.

Fast forward to that Vegas debate stage, where America saw two contenders as natural fighters and one yet to show whether he’s got it or not.

Sen. Elizabeth Warren, D-Mass., is unflinching in taking it to the field AND to corporate America. As a collegiate debate champion, she learned how to put others back on their heels by rising up on hers. In the days ahead she’s going to fight.

Sen. Bernie Sanders, I-Vt., is also a natural fighter bred from years of being dismissed and denigrated as a serious player; years of being told this is the way things are so shut up and deal with it. It’s safe to say no one is silencing Sanders now, and he’s going all out, fighting every step of the way.

Which brings us to Bloomberg, who needs to show he’s got another gear as a street fighter who ran the most difficult city in the world for 12 years after building one of the most impressive business empires.

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In short, he needs more punch, not punch lines, more verve and plenty more nerve.

As the Italian Stallion said of his rumble with Drago in Rocky IV, “To beat me, he’s going to have to kill me. He’s gonna have to have the heart to stand in front of me and to do that. He’s got to be willing to die himself.”

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Put simply, Bloomberg needs to start acting more like a New Yorker. New Yorkers are fighters. Democrats want a fighter.

To have a chance, any chance, they can’t possibly win without one.

CLICK HERE TO READ MORE BY ADAM GOODMAN