Donald Trump just can't get over President Biden ... repeatedly attacking him on the debate stage ... even though his opponent is Kamala Harris.
The former president ripped Biden several times during Tuesday's debate against Vice President Harris in Philadelphia, saying Biden's been so absent in the Ukraine war he wonders if POTUS is even alive.
Trump said Democrats threw Biden out of the race "like a dog" after a poor showing in a June debate against Trump ... and he says Biden's since spent his days sleeping or chilling at the beach.
Harris reminded Trump he's running against her not Biden ... and she often distanced herself from the Prez, with Trump trying to lump them together as the same candidate.
Trump also claimed "We have a President who doesn't know he's alive" ... hours after Biden was visibly at the White House.
Despite Trump's debate claims, Biden is still very much alive ... hosting the UCONN men's basketball team at the White House earlier Tuesday, in recognition of their second straight national championship.