At the same news conference where he took a swipe at Trump, Biden was asked by a reporter if he has been tested for cognitive decline.

“I’ve been tested and I’m constantly tested,” Biden responded, adding that “I can hardly wait to compare my cognitive capability to the cognitive capability of the man I’m running against.”

A Trump campaign Twitter feed played back the clip and asked, “Did Biden take a cognitive test? What were the results? Why is he getting frequently tested?”

Biden campaign advisers tell Axios’ Alexi McCammond and Hans Nichols that the testing Biden was talking about is the past 15 months on the campaign trail and that they see Trump’s attacks, in psychological terms, as “projection.” They also said Biden wasn’t previewing a new theme, just highlighting Trump’s attempt to distract from his own vulnerabilities.