Barack Obama accused Donald Trump of treating the US presidency like “one more reality show”, in a withering speech to the Democratic convention.
The former US president said his Republican successor “hasn’t grown into the job because he can’t”.
At the White House, Mr Trump hit back that he was only elected because of the “horror” Mr Obama left Americans.
On the third night of the Democratic conference, Kamala Harris accepted the vice-presidential nomination.
The grand finale of the four-night convention will see Democratic presidential nominee Joe Biden deliver a speech on Thursday.
The Biden-Harris ticket will challenge President Trump and his Vice-President Mike Pence for the White House in the election on 3 November.
The coronavirus pandemic has forced Democrats to abandon the cheering throngs and razzmatazz that are the hallmarks of the quadrennial party convention in favour of a virtual event of pre-recorded and live speeches.