PHILADELPHIA, July 27 (Reuters) - U.S. Vice President Joe Biden attacked Republican presidential nominee Donald Trump on Wednesday as an opportunist who has no clue about how to make America great or help working families.
Drawing chants of "Not a clue" from the floor of the Democratic Party convention in Philadelphia, Biden took Trump to task for his trademark reality TV slogan, "You're fired."
"When the middle class does well, the rich do very well and the poor have hope. He has no clue about what makes America great. Actually, he has no clue period," Biden, his voice trembling with emotion, said to cheers.
The vice president lauded the Democratic presidential nominee Hillary Clinton as a fighter who cares for struggling families.
Biden, 73, had considered running for the Democratic nomination against Clinton but ruled himself out last October, saying he and his family were not ready for a grueling campaign while still mourning his son Beau, who died of brain cancer.
Known for his foreign policy experience, Biden said Trump was unfit to be elected to the White House on Nov. 8.
"Let me say something that has nothing to do with politics. Let me talk about something that I am deadly serious about. This is a complicated and uncertain world we live in," Biden said, asking people to be silent while he finished his statement.
"The threats are too great, the times are too uncertain, to elect Donald Trump as president of the United States," he said.
During Obama's two presidential bids, Biden was often deployed on the campaign trail to try to win over white voters who could identify with his working background and direct manner of speaking.
See more of Biden through the years:
(Additional reporting by Amy Tennery, Emily Stephenson, Jonathan Allen, Susan Heavey, Doina Chiacu, Steve Holland and Frances Kerry; Writing by Frances Kerry and Alistair Bell; Editing by Peter Cooney and Howard Goller)