The new position is a reversal from statements Sanders and his aides have made throughout the campaign. Aides to Hillary Clinton cast the decision as a way to soften his gun position the day before Sunday's fourth Democratic debate.
"I'm pleased that this legislation is being introduced," Sanders said of Sen. Richard Blumenthal and Rep. Adam Schiff's proposal to take away immunity from gun manufacturers when their products are used in crimes. "As I have said for many months now, we need to look at the underlying law and tighten it up."
Sanders has declined to call the 2005 vote a mistake a number of times, citing the fact that he worries about the impact rescinding immunity would have on small, family-owned gun shops.
"If somebody has a gun and it falls into the hands of a murderer and that murderer kills somebody with the gun, do you hold the gun manufacturer responsible?" he asked at the Democratic debate in Las Vegas in October. "Not any more than you would hold a hammer company responsible if somebody beats somebody over the head with a hammer. That is not what a lawsuit should be about."
In supporting the legislation, Sanders also said he would propose an amendment to the bill that "would require the Commerce Department to monitor and report on the law's impact in rural areas on the availability of hunting supplies, including firearms, sold by non-negligent local gun stores."
Last year, however, Sanders aides said that if given the chance to vote for the bill again, he would likely vote the same way. Despite that history, Sanders' top aide denied that the change announced Saturday was a reversal.
"This is not a flip flop," said Jeff Weaver, Sanders' campaign manager. "This is consistent with the position he held earlier in the campaign."
Clinton's campaign does not agree.
John Podesta, Clinton's top campaign aide, tweeted Saturday
that the campaign "welcomes Senator Sanders' debate-eve conversion, reversing his vote to immunize gun manufacturers."
Guns have been a nagging issue for Sanders ever since he declared his candidacy last year. At first, he declined to talk about the issue at length, telling reporters in Las Vegas that he would talk about the issue when he chose to.
As the race heated up, Clinton and her aides began to hit Sanders on the issue, using it as a wedge against Sanders as he struggled to explain old votes at odds with the Democratic base's views.
Clinton released an ad last week
that lined the 2016 candidate up with President Barack Obama on guns and challenged Sanders to "pick a side" on the issue.
"It is time to pick a side," Clinton says in a not-so-subtle dig at Sanders. "Either we stand with the gun lobby, or we join the President and stand up to them. I am with him. Please join us."