A former adviser to President Bill Clinton said he’s concerned about 2020 Democratic presidential candidate Joe Biden’s mental acuity.

Dick Morris, who was Clinton’s political adviser and later campaign manager, argued that the former vice president’s memory lapses make President Trump’s reelection more likely.

“I don’t think that Biden has much of a chance of defeating Trump. I think that Biden is a very fragile candidate,” Morris told radio show host John Catsimatidis on Sunday. “He has risen from the dead, but the ashes still remain. I think he’s incredibly vulnerable on the Hunter Biden issue. I think his gaffes raise serious questions about his mental ability.”

Biden, 77, has often mixed up details in the stories he tells on the campaign trail, bringing scrutiny about his ability to be an effective counterpuncher to Trump.

“Biden should be required to have a test for Alzheimer’s disease. We can’t elect a president who has that deterioration of the brain setting in at the start of his term,” Morris said. “We’re entitled to know that. His personal inability to function will become more and more apparent, particularly on the debate stage. ... He’s becoming senile or coming down with Alzheimer’s.”

Biden’s doctor released a report on the former vice president’s health in December that said he is being treated for an irregular heartbeat, high cholesterol, acid reflux, and seasonal allergies. His doctor added that Biden was a "healthy, vigorous, 77-year-old male, who is fit to successfully execute the duties of the Presidency."

The report did not mention any declining cognitive ability or mental function.