KEENE, N.H.

In Bernie, they believe.

“Bernie’s been singing the same song of justice his whole life,’’ said Giselle Alexandria Snow, the Keene State College nursing student who introduced Bernie Sanders to the adoring crowd that filled the Colonial Theatre here in Keene on Tuesday. “I know no amount of money can buy out Senator Sanders.’’

It’s easy to smile at the cult-like devotion of young supporters who pack Sanders rallies and burst into 1960s-era song as they await their hero: “You say you want a revolution!’’

But deep faith in Sanders as a man of principle and integrity is key to his campaign, especially with young people. In Iowa, 84 percent of caucus-goers aged 17 to 29 supported Sanders.

Idealism is a wonderful quality. It flourishes most strongly in those who lack memory of what has gone before. Having never been burned by a politician they believed in, they are free to “feel the Bern.’’ And so they do.

Polling shows that Hillary Clinton is perceived as stronger than Sanders on every issue, from the economy and health care to immigration and terrorism. But doubts about her honesty undercut respect for her knowledge and experience. No excuses, here; it’s the price of personal decisions made, from the private e-mail server Clinton kept as secretary of state to the huge sums of money she took for speeches to Wall Street bankers.

What is known about Sanders suggests he can’t be bought and stands by his convictions. But there are other ways to assess honesty — like how candid he is about his ability to turn convictions into policy. The Washington Post editorial board called him out on this and he didn’t like it. But he owes it to supporters to do more than urge them to “think big.’’

Those who listen reverently to Professor Sanders lecture on Wall Street immorality and the influence of money on politics should apply some critical thinking to his pronouncements. If those evil economic forces are as potent as Sanders proclaims, how will he vanquish them?

President Obama helped bail out Wall Street and the auto industry. His top economic advisers came from the investment banking world. Yet, as others have noted, Obama’s political enemies still branded him a socialist who longed to redistribute wealth. And they thwarted much of what he hoped to accomplish in Congress. The Affordable Care Act, which falls far short of Sanders’ goal for health care reform, passed without a single Republican vote.

Imagine what those same political enemies would do to a president who, like Sanders, welcomes the “socialist’’ label and crows about his desire to shift wealth from rich to poor.

Sanders is asking his supporters to trust him when he says he can deliver free college tuition, single-payer health care, a $15 per hour minimum wage, affordable child care for all, and lower drug prices. How will he do it? By imposing a tax “on Wall Street speculation,’’ he said in Keene, as if that could happen with the wave of a presidential wand. By the way, he also plans to stop the Koch brothers and end institutional racism.

But, of course, he’s leading a revolution. If it carries him to the White House, Wall Street bankers will bow to the will of the people and start offering up their bonuses to help pay off some kid’s college debt. Republicans, too, will see the error of their ways, and stop trying to do what Sanders said they want to do: “cut Social Security, Medicare, and Medicaid, and give huge tax breaks to the wealthy.’’

In Bernie, his supporters trust.

He owes them more honesty about how hard it will be to deliver on his promises.

Joan Vennochi can be reached at vennochi@globe.com. Follow her on Twitter @Joan_Vennochi.