From the Atlantic article:
At the end of June, in the afterglow of a debate performance that would ultimately prompt President Joe Biden to end his campaign for reelection, Donald Trump startled his aides by announcing that he’d come up with a new nickname for his opponent.
“The guy’s a retard. He’s retarded. I think that’s what I’ll start calling him,” Trump declared aboard his campaign plane, en route to a rally that evening, according to three people who heard him make the remarks: “Retarded Joe Biden.”
The staffers present—and, within hours, others who’d heard about the epithet secondhand—pleaded with Trump not to say this publicly. They warned him that it would antagonize the moderate voters who’d been breaking in their direction, while engendering sympathy for a politician who, at that moment, was the subject of widespread ridicule. As Trump demurred, musing that he might debut the nickname at that night’s event, his staffers puzzled over the timing. Biden was on the ropes. Polls showed Trump jumping out to the biggest lead he’d enjoyed in any of his three campaigns for the presidency. Everything was going right for the Republican Party and its nominee. Why would he jeopardize that for the sake of slinging a juvenile insult? (A campaign spokesperson, Steven Cheung, said the nickname “was never discussed and this is materially false.”)