But as Sanders attempts to hitch himself to this inspirational group of teenage activists, he has a serious problem he needs to come to terms with: his track record voting in favor of some of the worst laws pushed by the gun lobby.

The most promising movement against gun violence in decades has a new friend in Washington: Sen. Bernie Sanders, who released a video last week promoting his meeting with the Parkland High students.

His lowest moment was in 2005, when he voted for a law that prevents victims of gun violence from suing gunmakers and sellers — even those who profit from the AR-15–style semi-automatic rifles used in many of the deadliest mass shootings of recent years. The timing of that vote was significant: It came a year after the Bush administration allowed a 10-year ban on assault weapons, introduced in the Clinton era, to expire.

The cost of ending that assault weapons ban, and shielding gunmakers from much of the basic legal accountability faced by any other US business, quickly became clear. Sales of semi-automatic rifles like the AR-15 went through the roof, and so did the number and frequency of massacres committed with them. By the time Sanders was seeking the Democratic nomination in 2016, parents of 6-year-olds killed in the Sandy Hook massacre were fighting in court to overturn the immunity law he supported.

Prior to his presidential run, guns were rarely a political obstacle in Sanders’ long political career. Pro-gun views are widespread in rural Vermont, a state with a long hunting tradition and virtually no firearms regulation. But they are anathema to the majority view of the Democratic Party — and Hillary Clinton and her supporters didn’t let him forget it in 2016.

Knowing this, Sanders finessed his vote by sending mixed messages. On some days, he’d say he stood by his controversial vote. "Do I think the victims of a crime with a gun should be able to sue the manufacturer? No, I don't," he told the New York Daily News in April that year.

On other days, he’d let it be known he was reconsidering. "I think we should take another look at that legislation and get rid of those provisions which allow gun manufacturers to act irresponsibly,” he said in Iowa in January 2016. He later cosponsored a Senate bill repealing the immunity.

Clinton pounced, accusing him of flip-flopping. She was right, and that should have damaged his reputation as a political renegade, but it didn’t. Compared to a former secretary of state and spouse of a former president, Sanders, with his wild hair and righteous pulpit-pounding, seemed a picture of authenticity. (Clinton flip-flopped too, but no one has ever celebrated her “authenticity.” That, however, was Sanders’ stock-in-trade.)

Sanders continues to stress that he’s no longer in the National Rifle Association’s good graces — he supports a return of the assault weapons ban — while saying, incredibly, that makers of AR-15–style semi-automatic rifles should be given a special form of legal immunity.

It was with this history that Sanders met with the amazing teens who not only survived the massacre at their high school in Parkland, Florida, but who are now leading the most promising movement against gun violence since Congress banned the making and selling of assault weapons 24 years ago.

I’d presume the Parkland teens hope that aligning themselves with Sanders will send a message to other mobilized students: that standing against the NRA is standing against a status quo that paves the way for school shootings. In challenging Clinton, Sanders also fought against the establishment — and the Parkland activists probably see Sanders as a natural ally.

But I’m also going to presume they would reconsider that if they were fully informed of Sanders’ gun record. Families of Parkland victims who seek justice are held back in part thanks to the gun immunity law the senator happily defended last year. And I'm presuming Sanders didn’t explain his gun record to them, for the same reason he didn’t explain it to Democrats during the 2016 primaries.

The greatest strength of these teenage activists is their unimpeachable credibility. Arguing against their anti-NRA and pro–gun control views means arguing against people who know more about death and violence than most middle-aged men. Theirs is not just an evidence-based argument — it is fueled, biblically speaking, by great vengeance and furious rebukes.

Aligning themselves with a man who gave legal protection to gunmakers, however, would be the first step in compromising that credibility. How can you be against the gun lobby when you’re standing with someone who helped that lobby win one of its greatest victories?

For Sanders, however, there’s nothing but upside. His next White House run will require a whitewashing of his gun record, and what better way of doing it than by aligning himself with young gun control activists whose credibility is unimpeachable?

Sanders’ flip-flopping on guns in 2016 was standard campaign politics. But this time is different. This time he’s threatening to compromise one of the most promising movements in a generation, all for his own political gain.

John Stoehr is a fellow at the Yale Journalism Initiative, a contributing writer for the Washington Monthly, and a U.S. News & World Report contributing editor.

