“Leadership is not yelling and screaming and intimidating,” said Cuban, the owner of the NBA’s Dallas Mavericks and “Shark Tank” star, addressing a raucous crowd at a Clinton rally in his native Pittsburgh. There’s a word people from Pittsburgh use for those who behave that way, he said: “Jagoff.” Cuban was dressed in jeans and a T-shirt with a picture of Batman and the words “I got this.”

“Is there any bigger jagoff in the world than Donald Trump?” Cuban asked as the crowd roared. Clinton reacted with delight, hugging Cuban on stage. Former President Bill Clinton saluted in Cuban’s direction after his remarks, then crossed the stage to shake his hand.

Cuban’s first appearance on Clinton’s behalf came after ongoing conversations with the campaign, though earlier this year he suggested he might back Trump if Clinton chose Senator Elizabeth Warren as a running mate, and said he would be open to serving as a running mate to either Clinton or Trump. Plans for Saturdays’s appearance came together after a telephone call from Cuban to campaign chairman John Podesta on Thursday, before Clinton formally accepted her party’s nomination, saying he was ready.