Hell hath no fury like Bernie’s millennials if they are thwarted.

Bernie Sanders has the youngest, biggest and most passionate crowds on the eve of the Iowa caucuses, and in Cedar Rapids on Saturday night, he primed his supporters to prepare for war — and not just against President Trump.

“We are taking on the entire political establishment,” he told the 3,000-strong crowd.

“Both the Republican establishment and the Democratic establishment . . . This is the political reality of the moment.”

Moments before, the Des Moines Register and CNN seemed to confirm his team’s paranoia by spiking a crucial poll expected to reflect his rising ascendancy.

The poll cancellation at the 11th hour simply came down to a complaint from Pete Buttigieg’s campaign after his name was accidentally left off one of the questions.

But it fed nicely into the outsider mentality Sanders is cultivating: one man standing against a rigged system.

As Joe Biden pokes people in the chest in lackluster rooms full of gray heads and empty chairs, Sanders has tapped millennial energy in almost Trumpian events across Iowa where the crowd chants “Bernie” and swoons when he calls his wife of 32 years “the love of my life.”

“Hashtag, goals,” gooed Talia Wlcek, 21, at the Cedar Rapids stadium Saturday night, after the reference to Jane Sanders. “That’s so sweet.”

On the eve of Monday’s caucuses, as Sanders rides high in the polls, the Democratic establishment “fears the Bern” more than ever.

They’ve just changed the rules to allow billionaire Michael Bloomberg “to buy his way onto the stage” as Sanders’ warm-up man, filmmaker Michael Moore, puts it.

Hillary Clinton has spent the last week saying “nobody likes” Sanders and effectively blaming his supporters’ for her 2016 election loss.

There is even a conspiracy theory that House Democrats timed the Senate impeachment trial deliberately to keep Sanders in Washington to dent his momentum in Iowa.

But, with charismatic proxies such as his socialist ally, Rep. Alexandra Ocasio-Cortez, pulling big crowds on his behalf, Sanders never faltered.

The 78-year-old Vermont socialist is more popular since his heart attack three months ago, and his advanced age has become an oddly wistful campaign pitch.

“He may be 78 years old but we’d like to make him 46,” Nina Turner, national co-chairwoman of his campaign, told the Cedar Rapids crowd, promoting whoops and cheers.

In the 18-to-49 age group, Sanders is polling 32 points ahead of Joe Biden, who was languishing at 7 percent in last week’s Monmouth University poll.

However, the positions were reversed in the 65-plus age group, with Biden at 37 percent to Sanders’ 9 percent.

Honeymooning in the Soviet Union and praising communist dictators is a political death sentence for anyone who recalls Stalin and Pol Pot, but for a younger generation, ignorance is bliss.

Sanders’ $50 trillion in spending might dwarf the promises of his rivals, but idealism doesn’t have a price.

The biggest cheers of Saturday night greeted his promise to cancel “all student debt in America” (price: at least $1.5 trillion) and “legalize marijuana in every state.”

He knows his audience.

He had enlisted cult Grammy Award-winning band Vampire Weekend to play at his rally, a sure-fire youth draw for a free concert on a winter’s night. But there was no doubting he has struck a chord with a new generation hungering for consistency and authenticity.

“He is the most dedicated to his ideas, and climate, anti-war stuff,” said home-schooled local Alex Niermann, who turns 18 in April and will vote in his first election for Sanders.

“He’s been at it for half a century. He doesn’t waver and he doesn’t take any money.”

“He’s so different from everyone else,” said Alex Kelly, 22, an art student at Upper Iowa University.

“I never really paid attention to politics before . . . but he stands for a lot of the things I care about. He doesn’t seem fake.”

Her classmate, Kjerstin Miller, 24, said she “grew up LGBT as the only liberal in a house of conservatives . . . I love the consistency of Sanders’ career. He wants to make this country better for everyone, black, white, gay, straight, autistic, neurotypical.”

Sanders is the ultimate political outsider, fighting against a corrupt political establishment that has rigged the system.

In other words, his authenticity and populist appeal is the mirror image of Donald Trump’s.

Sanders rails against “Wall Street and the insurance companies and the drug companies and the fossil-fuel industry and the military-industrial complex . . . and the whole damn 1 percent.”

Trump fights the “Swamp,” the “Deep State,” “fake news media,” globalists who ship your jobs to China, and Shifty Schiff and his “sham impeachment.”

Sanders is running as an outsider in an era that spurns insiders.

But, the irony is, so is the president, even after three years in power. Impeachment is the gift that keeps on giving.

Caution is not racism

As the first suspected case of the coronavirus emerges in New York City, and scientists warn of a global pandemic, now is not the time to play the racism card.

“This has been used as an opportunity to bash Chinese and other Asian people,” claims Buzzfeed.

“Viral diseases don’t have ethnic, racial or national characteristics,” says Tim Soutphommasane, one-time Australian discrimination commissioner.

No, but the virus originates in China. It is not racism to block flights from China or require people returning to self-quarantine for 14 days.

Iowa’s big moment

Like so many Iowans, Mike Farley is losing sleep trying to decide who to caucus for Monday.

The 68-year-old retired physician’s assistant from Des Moines has decided Elizabeth Warren is the best of the nine candidates he has met in person.

“I like the fact she wants to fight corruption because corruption holds the key to everything.”

But he also is drawn to Bernie Sanders.

“Every night when I go to bed, I lie awake wondering is this the right choice?” he says.

Iowans do their due diligence, and so they should because their vote has an outsized influence. The winner in Iowa has turned out to be the Democratic nominee in five of the past seven presidential contests.