US vice president Joe Biden has questioned Donald Trump's "moral centre" as a result of the Republican presidential candidate's comments about America's housing collapse.
At a rally for Hillary Clinton at Drexel University, Philadelphia, Mr Biden said that Mr Trump had bragged at last night's presidential debate about profiting from the failed housing market.
He said Mr Trump's policies are not helpful for the country, calling the candidate is "painfully uninformed".
"This is a guy who said it was good business for him to see the housing market fail," Mr Biden said. "What in the hell is he talking about?"
At the debate, Mrs Clinton said Mr Trump had rooted for the housing collapse in 2006 because he saw it as a way to go in and make money.
Mr Trump responded: "That's called business, by the way."
Mr Biden said that Mr Trump "brags about gaming the system and bankruptcy" while "sitting on top of Trump Tower in a semi-golden palace".
"Every president I have served with, including the Republicans, has had a moral centre about what it means to be an American," he said.
Referring to meetings he has had with Nato allies, Mr Biden said Mr Trump's campaign is damaging America's standing in the world, and that world leaders have expressed concern over a Trump presidency.
Mr Trump "does not have the basic fundamental sensibilities and values that almost every American politician, left, right and centre, I know, has," Mr Biden said.
Several students interviewed at the rally said they were still on the fence.
"This is my second time voting and already there are no candidates I'm interested in," said Matt Goldforb, 22, an electrical engineering major from Melville, New York.
Nursing student Danielle Sobieski, 18, said she is "honestly scared" about the state of politics.
"I don't want to make the wrong choice, and, right now, both seem like they'd be fine and either could be the next president," the central New Jersey resident said.
She said she will wait until November to decide on her choice.
Mr Biden acknowledged students' political frustrations, but urged them to support Mrs Clinton.
"I know (students) are not overjoyed about the choices. I know they think that Hillary didn't do A, B, C or D, I know, but, my Lord. My Lord. What are we going to do?" he said.