Biden's first campaign appearance on behalf of the Democratic nominee blended blue-collar outreach with stinging rebukes of Trump from a man who, Biden reminded the crowd, travels with his own copies of the nation's nuclear weapons codes.
"It used to be a basic bargain," that hard work could mean entry into a stable middle-class life, Biden said, voicing a theme of economic angst that Clinton has sought to put at the center of her second run for the White House.
The Republican nominee is utterly unfit to oversee American national security and "has already made this country less safe" with his incendiary rhetoric, Biden charged.
Biden noted Trump’s stated admiration for Russian President Vladimir Putin, who Biden said has a goal of destroying the NATO alliance.
“He would have loved Stalin,” Biden added, to laughter.
But alongside the attacks came an appeal to the sorts of white working-class voters Trump has helped to peel away from the Democratic Party. Biden, whose decades in office were built on the support of blue-collar Democrats, made clear that he sees it as his political mission to try to repatriate many of them.
Scranton, where Biden lived until he was in grade school, is filled with people defined by "grit, courage and determination to never, ever give up," the vice president said. "They deserve someone who not only understands them. They deserve someone who will be with them."
Biden spoke about twice as long as Clinton, delivering a sometimes wandering but always fond endorsement of Clinton as a seasoned public servant who "gets it" about economic changes that have left some parts of the country behind.
Toward the end, he told the crowd that he had "tried your stamina," as Clinton looked on, laughing.
An NBC-Wall Street Journal-Marist poll released last week found Trump leading by 16 percentage points among white registered voters without college degrees, but he trailed by 21 points among white college graduates and by a 93-point margin among African Americans.
(For reference, the exact margins were 50-34 Trump-Clinton among non-college whites, 53-32 among college-grad whites and 94-1 among African Americans).
That all added up to an 11-point overall advantage for Clinton, 48 to 37 percent. Her lead is narrower in Ohio (between 4 and 5 points in recent surveys), but with the exact same pattern — Trump leads among non-college-educated whites, but Clinton’s edge with college-graduate whites and others puts her ahead.
For her part, Clinton said she understands that "some of you may have friends up here in northeastern Pennsylvania who are thinking about voting for Trump."
She smiled as some in the audience booed the mention of the businessman's name.
"I know," she said. "Friends should not let friends vote for Trump."
Clinton played up her own roots in Scranton, her father's home town and the city she says allowed her grandfather, a lace mill worker, to begin the family's ascent into a comfortable middle-class life.
"Wherever life takes me, I always remember I am the granddaughter of a factory worker and the daughter of a small business owner," Clinton said to cheers from an audience of about 3,000 at an indoor sports field.
"No matter what Donald Trump says, America is great and the American Dream is big enough for everyone to share in its promise."
Clinton's campaign released her 2015 tax returns Friday, showing that she and her husband, former president Bill Clinton, earned nearly $11 million last year, much of it from paid speeches. She launched her second presidential campaign in April 2015 and stopped giving paid speeches then.
Clinton and Biden both ran unsuccessfully for the Democratic nomination in 2008, and Biden considered challenging her again this time. He removed himself from contention last fall, saying he had concluded that there was no way for him to catch up to the longtime front-runner.
In addition to employing Biden as an ambassador to Rust Belt voters who once were reliable Democrats, Clinton said Monday that if elected, she will ask him to continue his work on a "moon shot" mission to cure cancer.
Overall, Trump’s strategy relies on maximizing his advantage with white working-class voters to offset Clinton’s strength with other groups, particularly nonwhite voters. Non-college-educated whites make up a greater share of the electorate in Pennsylvania, as well as Ohio and Michigan, making them states in which Trump supporters hoped he could make inroads. At this point, polls show Trump trailing in all three states, with his leading margins among non-college-educated whites failing to balance out losses in other groups.
One challenge for Trump is a potential ceiling on growth — non-college-educated whites have already supported Republicans by a wide margin, leaving Trump’s campaign to strive for even more lopsided support or to inspire a spike in turnout among a group that votes at lower rates than white college graduates. Trump is also struggling on both fronts. Mitt Romney won whites without college degrees by 25 percentage points over Obama in 2012, according to the national exit poll, identical to Trump’s margin over Clinton in a Washington Post-ABC News poll earlier this month.
Meanwhile, Clinton held a six-point edge over Trump among college graduates, a group Romney won by 14 points in 2012.
Scott Clement in Washington contributed to this report.