"Every single false charge, every single baseless accusation is a simple attempt to get you to focus on something other than what's affecting your family and your country," said Biden, who was cheered by some 6,000 people packed into a sports arena in the blue-collar city where he lived until he was 10.
"It's good to be home!" said the Delaware senator, who was joined on stage by former President Clinton and Sen. Hillary Clinton - the former Democratic presidential candidate who has her own roots in Scranton, where her father grew up and is buried.
The battered economy may be helping Obama in Pennsylvania, where he has surged ahead in polls over the past few weeks. A daily tracking poll conducted by Muhlenberg College has shown Obama with a double-digit lead over McCain since Oct. 3.
If Obama and Biden win Pennsylvania, Sen. Clinton predicted Sunday, "there's no way they can lose the White House."
Clinton beat Obama in the Pennsylvania primary by 10 percentage points, in part by appealing to the socially conservative, blue-collar voters in Scranton and many other parts of the state. Biden's counterpart, Republican Alaska Gov. Sarah Palin, is scheduled to campaign in the city on Tuesday.
Biden on Sunday cast McCain as out of touch with the concerns of everyday Americans who are worried about their jobs and the declining values of their homes. He said McCain doesn't know how to get the nation's economy back on track and would simply continue the policies of President Bush.
"Nothing less than our prosperity and our security is on the ballot," he said.
At an Obama rally in Roanoke, Va., later Sunday, Bill Clinton said Bush's response to the financial crisis is helping Obama's campaign.
"The administration keeps plowing an Uzi's worth of bullets into the McCain-Palin ticket every time they have something else go wrong," Clinton told an evening rally of several hundred people gathered at Roanoke's downtown Market Square. "It's good politics for us."
Clinton praised the Democratic candidate's plan for financial recovery and his proposals for health care reform, an issue that he said nobody has taken on "since Hillary and I got our brains beat out trying to fix."
In Pennsylvania, Biden defended a comment he made in an ABC interview last month in which he said the wealthiest Americans should show their patriotism by paying more in taxes. The Obama campaign has said it plans to hike taxes on people earning more than $250,000, but would cut taxes for those making less. Republicans have criticized Biden over the remark.
Accusing businesses and wealthy individuals of using "offshore tax loopholes" to hide $100 billion a year in income, Biden told the crowd Sunday, "It is unpatriotic when you earn your money in the United States of America and you hide it offshore to avoid taxes, making sure YOU have to make up the difference."
His voice rising, the Delaware senator shouted: "It is unpatriotic to take $100 billion offshore and not pay your taxes! That is unpatriotic! So I don't need a lecture on patriotism! I've had it to here!"
The McCain campaign pointed out that Biden and both Clinton had raised questions about Obama during the Democratic primaries.
"As voters in northeast Pennsylvania continue to raise serious questions about Barack Obama's judgment and character, it is befitting that they will now hear from the three leading voices who sounded the alarm on the risk of an Obama presidency," said McCain spokesman Paul Lindsay.