The former president said in a Truth Social post that Kamala Harris had "terrible pole numbers against a fine and brilliant young man," referring to himself.
With Joe Biden out of the race, Donald Trump has become the oldest presidential nominee ever.
Trump's now facing off against Kamala Harris, 59, a woman decades younger.
On Monday, Trump called himself a "fine and brilliant young man" while criticizing Harris.
I'd offer up a "Black don't crack" but I think all the time about what 8 years in office did to Obama. They must have a hyperbaric time chamber attached to the Oval office.