NBC News' Sahil Kapur reports that Trump has had trouble making his voters frightened of Biden, which is why he's now turning his focus to vice presidential nominee Kamala Harris.
"In attacks that critics decry as sexist and racist, Trump has sought to convince voters that supporting him is needed to stop Harris, whom he paints as too liberal and as being groomed to usurp the presidency," he writes.
Stephanie Cutter, a co-founder of the consulting firm Precision Strategies, tells Kapur that Trump is trying to run "a combination of trying to make Biden look feeble and doing some race-baiting on Kamala."
However, she also predicted that both attacks would flop.
"He's had a hard time getting anything to really stick to Joe Biden -- whether it's 'sleepy Joe' or 'liberal Joe,'" she said. "Now he's suggesting performance enhancing drugs. Nothing is sticking because people have a pretty good sense of Joe Biden and what is at his core."
Republican consultant Matt Gorman shared a similar assessment.
"People vote for the presidential nominee, not the vice presidential nominee," he said. "The focus needs to be on defining Joe Biden."