Stephen Colbert late Monday mocked 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 for a tweet that he was a "stable genius" and "like, really smart."

During "The Late Show," Colbert said being "like, really smart" is not the same thing as "being really smart."

Colbert added that people who are mentally stable "generally don't announce it."

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“We all know geniuses spend most of their time talking about how smart they are," Colbert joked.

"I believe it was René Descartes who said, ‘I think, therefore I am, like, really smart.’”

His comments come after Democrats and the media have raised questions about Trump's mental fitness for office in the wake of revelations from a new book detailing the first year of the Trump administration.

Trump over the weekend tweeted about his mental stability.

"Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart," Trump said.