WASHINGTON — Sandy Phillips, who lost her 24-year-old daughter, Jessi, in the mass shooting at a movie theater in Aurora, Colorado seven years ago, can’t forgive Sen. Bernie Sanders, now a top-tier candidate for the 2020 Democratic presidential nomination.

Sanders, in the House at the time, supported a 2005 law backed by the National Rifle Association granting gun manufacturers broad legal protections and was one of 59 Democrats to vote for the legislation in the GOP-led House. Sanders and Rep. Tim Ryan of Ohio are the only Democratic presidential candidates to have voted for that bill, which Phillips said nearly bankrupted her family.

Phillips says she called Sanders during the 2016 presidential primary campaign when he was competing against Hillary Clinton, asking for an explanation of his vote.

“He was like ‘I’d love to talk to you about this, but I’m really busy,’” Phillips told NBC News, describing him as “extremely dismissive and arrogant.”

In early 2016, days before the Iowa caucuses, Sanders, a Vermont independent, announced he would co-sponsor a repeal of the law as he faced criticism over his position. Weeks later, he contradicted himself, saying gun crime victims should not be able to sue — only to reverse course again days later during a debate by saying, “They have the right to sue.”

Phillips and her husband had sued Lucky Gunner, the online retailer that sold her daughter’s killer 4,000 rounds of armor-piercing ammunition over the internet without a background check. Yet because the law granted gun retailers unique legal protections, the suit was dismissed. Phillips not only had to pay her own legal fees, a judge ordered her to pay Lucky Gunner $200,000 to cover its legal expenses.

Phillips’ story reveals a potential political liability for Sanders, who has at times backed the NRA’s agenda over his decadeslong congressional career. In addition to his support for legislation limiting lawsuits on gun-makers, Sanders also voted against a 1993 bill that would have established national background checks.

He now faces a large, diverse primary field and an activist party base empowered by a youth-driven demand for new gun safety measures — seen in the student-led demonstrations after the 2018 mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida.

Sanders is the top pick for likely Democratic primary voters age 18-29, according to a new Harvard University poll; and exit polling from the 2018 midterm elections found gun policy ranked as second only to health care as a top concern for Democratic voters.

The Sanders campaign did not dispute Phillips’ account of the phone call. “Bernie has campaigned tirelessly for common sense gun safety legislation,” the Sanders campaign said in a statement to NBC, noting his co-sponsorship of bills including bans on assault weapons and 3D-printed guns and restricting high-capacity magazines.

“Bernie believes that there is a movement in this country coming together that will overcome the influence of the NRA” and he will “take on the NRA” as president, the statement said.

While Sanders’s campaign also emphasized his support for universal background checks and a D- minus rating from the NRA, earlier in his career Sanders repeatedly opposed legislation establishing a national background check system and voted against federal funding into gun violence prevention. Sanders only recently reversed his long-held positions on guns, including his defense of the 2005 law.

Some other Democratic 2020 candidates, namely New York Sen. Kirsten Gillibrand, who previously had an A- rating from the NRA, have also changed position on guns. She did so after a 2009 meeting with the parents of a Brooklyn teenager killed by a stray bullet. Other Democratic presidential candidates are calling for new gun safety measures, with candidates backing legislation like universal background checks and assault weapons bans.

All of which puts Sanders, an unapologetic progressive on economic issues, to the right of many Democratic rivals on the subject of guns. He is the only senator currently running for president who did not sign a March letter demanding Senate hearings on the first gun safety legislation passed by the House in a generation.

Gun control advocates critical

Shortly after Sanders entered the 2020 campaign in February, Phillips and Shannon Watts, a founder of the gun control group Moms Demand Action, were among those dinging him on Twitter.

Sanders, Watts tweeted, “has historically sided with lobbyists” on guns and failed to even mention the issue in one of his campaign launch videos.

“We told him, 'The tide will turn and you should be on the right side of history now — not later.' He chose later,” said Phillips, in a later phone interview from Texas, where she was preparing to sell her home after, she says, her failed lawsuit “ruined us financially.”

Still, it’s clear that Sanders has sought to distance himself from his pro-gun past. NBC News found footage of Sanders at two March 2018 gun control rallies, and he also met with current and former Parkland students who came to Washington in early 2018.

The Sanders campaign released a video shortly after he announced his candidacy highlighting screenshots of a 1988 article on his opposition to assault weapons.

Two top leaders of the Giffords PAC — the group founded by Gabrielle Giffords, the former Arizona congresswoman who became a gun control advocate after being shot and nearly killed — said Sanders has come a long way on the issue. “He doesn’t want a repeat of 2016,” said the group's executive director, Peter Ambler.

Others are skeptical that a candidate who, as recently as 2013, expressed skepticism about the efficacy of stricter gun laws in preventing mass shootings will really be a champion for the cause.

Following the Newtown shootings, Sanders voted in favor of a failed 2013 bill to expand background checks. Still, he also said that even “the strongest gun control legislation” will not “have a profound effect on the tragedies we have seen,” according to the Washington Post Fact Checker. He also said that guns “are not one of my major issues.”

Watts of Moms Demand Action told NBC News said Sanders is not among a number of 2020 Democratic presidential hopefuls who’ve reached out seeking volunteers or to speak at local events. “I don’t believe he has explained" where gun control "falls on his list of priorities,” she said of Sanders' changing position on gun control.

The Record

Representing a state with a strong hunting culture, Sanders has spent most of his career as a strong supporter of gun rights.

He voted repeatedly against the 1993 Brady Bill that created the nation’s background check system. In December 2015, after launching his presidential bid, he urged funding research into firearms injuries, after opposing it in the late 1990s. Sanders also voted to close the “gun show loophole” in 1999.

The 2005 gun manufacturer immunity law may be most problematic for Sanders.

Dan Gross, president of the Brady Campaign to Prevent Gun Violence, has said it ushered in “a deadly decade of unchecked gun industry negligence.”

“It’s not something we’re going to forget,” Phillips said of Sanders’ long record of support for the law.

Sanders long held the same position as the National Rifle Association, which argued manufacturers shouldn’t be held responsible for the actions of violent criminals who use their guns.

Critics say the gun industry made itself liable for some mass shootings when, amid a decline in hunting-related revenue, it chose to invest heavily in marketing to young men weapons intended to inflict mass casualties on the battlefields of Vietnam.

“I have to wonder if they would have been able to engage in those marketing practices if they didn’t know they were protected” by the immunity law, Mark Barden, who lost his first-grade son, Daniel, in the 2012 Sandy Hook shooting, told NBC.

In a July 2015 interview on CNN, Sanders defended his vote for the law by saying that blaming gun manufacturers for mass shootings is the same as holding a hammer manufacturer liable for misuse of the tool.

But even after sponsoring a repeal of the law, Sanders seemed to defend it. In a March 6, 2016, primary debate, Sanders suggested only gun manufacturers who knowingly sell a gun under “suspicious” circumstances should be held liable. The comments prompted praise on Twitter from the NRA, which called Sanders “spot on.”

When asked if Sanders now supports the ability of the Sandy Hook families to sue, senior advisor Jeff Weaver said the candidate supports allowing the suit to proceed.

"Deceptive marketing of assault weapons in violation of state law is certainly the type of bad conduct for which Bernie believes companies should be held accountable,” said Weaver.

Gun safety advocates including Ambler, the Giffords director, say they will be “looking closely” to make sure all “candidates come down in the right place” on gun safety.

“One of his calling cards is his passion in taking on special interests. In 2016, some voters were confounded that that passion didn’t seemingly extend to taking on the NRA and the firearms industry,” said Ambler.

“I just want to understand,” Watts said. “Is it a priority?”

Phillips put it bluntly: “He’s not good on guns. People who are in this issue know that.”