Former Vice President Joe Biden Joe BidenSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE said Thursday that he believes President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE would be “abdicating the responsibility of the presidency” if he cites the Fifth Amendment in an attempt to avoid speaking with special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE.

If Trump "takes the fifth," he could cite constitutional protections against self-incrimination to avoid an interview with Mueller.

Biden told MSNBC’s Andrea Mitchell that it’s “abhorrent” that “a president of the United States says, 'I take the Fifth because I might incriminate myself.'”

Biden’s remarks come one day after he told CNN’s Chris Cuomo that he would advise Trump not to sit for an interview with Mueller because he “has some difficulty with precision.”

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Trump has publicly said he’s willing to sit for an interview with Mueller, and would do so under oath. But Trump's lawyers are reportedly urging the president not to sit down with Mueller over concerns he could open himself up to a charge of lying to investigators during the interview.

Mueller is leading a criminal investigation into Russian meddling in the 2016 election. The probe has thus far led to two indictments and two guilty pleas.

Biden said Thursday that, as president, Trump should be able to answer questions about Russians attempting to interfere in American elections. Biden called it “one of the most serious security breaches that’s occurred in American history.”

“I can’t fathom why the president, just as a patriotic American, let alone as president, would not be looking for every single bit of data and evidence that would show what they were doing and what they’re continuing to attempt to do,” he said.

Biden, 75, is considered a potential Democratic candidate for the presidency in 2020. On Thursday, he said he has "plenty of time" to consider whether to run, but said he's focused on Trump and Republicans causing an "erosion of the moral fabric" of the country.