A fiery Vice President Biden on Tuesday tore into Republican nominee Donald Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE for his performance during Monday's presidential debate, saying it proves he’s unfit to occupy the White House.

Speaking at a rally in Philadelphia, Biden blasted Trump for claiming to be “smart” for not paying federal income taxes and boasting that the housing collapse helped his business.

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“He acknowledged that he didn’t pay taxes because, he said, because he’s smart — makes him smart,” Biden told the crowd at Drexel University.

“Tell that to the janitor in here who’s paying taxes,” he continued, his voicing rising. “Tell that to your mothers and fathers who are breaking their neck to send you here, paying their taxes.

“No, I really mean it. It angers me," Biden said, adding that Trump is "painfully uninformed" about what it means to serve as president.

The vice president then brought up the GOP candidate’s retort to Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE that hoping for a housing collapse was good business sense.

“What in the hell is he talking about?” Biden said.

The vice president is seeking to fire up voters after Monday night’s debate, a badly needed victory for Clinton, the Democratic nominee.

Polls showed a close race going into the debate between Clinton and Trump. Now, Clinton’s team is taking a victory lap with a series of rallies in battleground states designed to ramp up voter enthusiasm.

The vice president is a top surrogate for Clinton, especially in Pennsylvania — his home state — and among white working-class voters, with whom Trump is popular.

Biden acknowledged that Clinton’s campaign hasn’t energized young voters like President Obama’s did.

"I know they are not overjoyed about the choices,” he said of students at the Philadelphia university. “I know they think Hillary didn't do A, B, C or D."

But Biden said Trump’s claims show he’ll throw the middle class under the bus if he’s elected president.

“Ladies and gentlemen, you know, he does not have the basic values that almost every American politician — left, right and center — have,” the vice president said. “They disagree on how to make things better for people. But they don’t take pleasure from ‘you’re fired.’ ”

He contrasted Trump’s worldview with that of Clinton, who he said is grounded by her middle-class upbringing in Illinois.

“I tell you what, if this choice isn’t clear — oh, Lord,” he said.

In addition to Biden’s Philadelphia rally, Clinton is hitting the campaign trail in North Carolina, a battleground state where polls show she is running neck and neck with Trump.

Vice presidential nominee Tim Kaine Timothy (Tim) Michael KaineTrump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court Barrett seen as a front-runner for Trump Supreme Court pick MORE is campaigning in Florida, and former President Bill Clinton William (Bill) Jefferson ClintonGOP brushes back charges of hypocrisy in Supreme Court fight Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE is set to headline a rally in Ohio.