Trump, criticizing aid to Ukraine, called Volodymyr Zelensky "one of the best salesmen in history"

"They must return the money to us. Give them money on credit. Or issue an invoice for 60 billion. I tell you, Zelensky is one of the best sellers in history: every time he comes, he returns home with $50-60 billion."

In turn, Biden responded to Trump's constant criticism of his age:

"One candidate for the presidency of the United States is too old and mentally unfit to be president. The other is me," Biden joked about the 77-year-old Trump.