Democratic presidential front-runner Hillary Clinton on Sunday once again attacked rival Bernie Sanders over the issue of gun control, but instead of hitting him for being on the wrong side of the debate, she accused him of "flip-flopping" to the right one.

Just hours before what is becoming an increasingly critical Democratic debate, Clinton took to the Sunday talk show circuit, during which she called out the Vermont senator for his newly-expressed support of ending legal immunity for gun manufacturers and closing other "loopholes" in the background check system.

"He flip-flopped last night," Clinton told host George Stephanopoulos on ABC's This Week, referring to Sanders' new support of bills introduced in the Senate and the House by Rep. Adam Schiff and Sen. Richard Blumenthal, ABC News reported.

"I'm delighted that he has had a change of heart. I think that's all for the good," Clinton added. "I welcome Senator Sanders moving on one of the issues he was wrong on. I hope he will continue to move." Clinton made similar comments on CNN's State Of The Union.

Sanders said Saturday that he supports legislation that would weaken a 2005 law protecting gun manufacturers and dealers from lawsuits when their firearms are used in crimes. His vote for the law, the Protection of Lawful Commerce in Arms Act, has been a sore spot for gun control activists, according to Bloomberg.

"I'm pleased that this legislation is being introduced," Sanders said in a statement, CBS News reported. "As I have said for many months now, we need to look at the underlying law and tighten it up."

Sanders' statement could provide some cover during Sunday night's debate in Charleston, S.C. after Clinton earlier this week called him "a pretty reliable vote for the gun lobby," according to CNN.

For his part, Sanders responded to Clinton's flip-flop charge by saying that it's a matter of him gaining ground in recent weeks. "I understand that Secretary Clinton and her campaign understands that, you know, they're losing ground. ... So I think in the next two weeks, you're going to see a lot of nonsense being thrown around," Sanders said on NBC's Meet the Press, The Washington Post reported.