President Donald Trump questioned Democratic candidate Joe Biden‘s cognitive ability once again and called for a drug test for both candidates before the first presidential debate next month.

“We are going to call for a drug test,” Trump told the Washington Examiner. “It wasn’t that he was Winston Churchill because he wasn’t, but it was a normal, boring debate. You know, nothing amazing happened.”

Trump accused Biden of using a drug before entering into a debate with Sen. Bernie Sanders (D-Vermont) during the March debate, asserting that Biden’s debating suddenly improved on that specific day.

“I don’t know how he could have been so incompetent in his debate performances and then all of a sudden be OK against Bernie,” Trump said. “My point is, if you go back and watch some of those numerous debates, he was so bad.”

“He wasn’t even coherent. And against Bernie, he was. And we’re calling for a drug test.”

Trump, however, did not suggest any evidence to his claims.

The president also requested a drug test before a third presidential debate with then-Democratic candidate Hillary Clinton in 2016, which did not happen.

The first presidential debate will take place in Cleveland, Ohio, on Sept. 29.