Democratic presidential candidates Hillary Clinton and Bernie Sanders spar during the fourth Democratic presidential debate in Charleston, S.C. (AP Photo/Mic Smith)

Democratic presidential candidate Bernie Sanders’s campaign strongly dismissed former secretary of state Hillary Clinton's accusation that he has been disloyal to President Obama, which she charged during Sunday night’s Democratic debate amid a heated exchange about her fundraising on Wall Street.

“He has been very, very supportive of President Obama and campaigned for President Obama twice,” campaign strategist Tad Devine said Monday. “It’s part of a series of attacks that they’re making that don’t have a lot of credibility. We could have a debate about real substance, real issues…but they don’t want to have that debate.”

“I think one of the things we’re trying to do is avoid getting sucked into whatever they want to talk about on any given day. Our view on a lot of this stuff is it’s just not credible,” Devine added.

After the Vermont senator hit Clinton on her ties to Wall Street during the debate Sunday, Clinton launched into an attack centered on Sanders’s previous criticisms of Obama, a political play many strategists believe was intended to sway black voters in South Carolina.

Obama, she said, had also raised huge sums of money from the financial sector but nonetheless sought to expand Wall Street regulations once in office.

“Where we disagree is the comments that Senator Sanders has made that don't just affect me -- I can take that -- but he's criticized President Obama for taking donations from Wall Street, and President Obama has led our country out of the great recession,” she said.

“Senator Sanders called him weak, disappointing. He even, in 2011, publicly sought someone to run in a primary against President Obama,” she continued. “Now, I personally believe that President Obama's work to push through the Dodd- Frank and to sign it was one of the most important regulatory schemes we’ve had since the 1930s.”

At the Jan. 17 Democratic presidential debate in Charleston, S.C., Bernie Sanders glared at Hillary Clinton when she accused him of being disloyal to President Obama. (NBC/YouTube)

Soon after Clinton's comments on stage, her campaign sent reporters a press release linking to several YouTube clips featuring Sanders criticizing the president, including one from 2011 of Sanders musing about finding a progressive candidate to challenge the president's 2012 reelection bid on the Thom Hartmann Radio Program.

"One of the reasons the president has been able to move so far to the right is there is no primary opposition to him,” Sanders said at the time. “I think it would do this country a good deal of service if people start thinking about candidates out there who begin contrasting what is a progressive agenda as opposed to what Obama is doing.”

Sanders’s facial expression as Clinton criticized him caused a splash on social media, inspiring videos and gifs that circulated widely.

Sanders himself pushed back aggressively on stage Sunday.

“In 2006 when I ran for the Senate, Senator Barack Obama was kind enough to campaign for me, 2008, I did my best to see that he was elected and in 2012, I worked as hard as I could to see that he was reelected,” he said. “He and I are friends. We've worked together on many issues. We have some differences of opinion.”