SCRANTON -- The last time Barack Obama was in Scranton he considered adding an apostrophe to his campaign signs -- O'Bama -- to attract votes in the heavily Irish blue-collar city. Instead, yesterday, he added something more authentic: Delaware Sen. Joseph R. Biden Jr., a city native who is half-Irish and all hometown-proud.

Scranton is at the heart of the working-class America that traditionally makes up the Democratic support base. Here, IrishCatholicDemocrat is considered a single word, and Mr. Obama is counting on Mr. Biden, a plain-spoken Catholic Democrat, to bring along the votes he needs in Pennsylvania and in blue-collar America at large.

It was a smart choice, said Scranton residents of both parties.

Mr. Obama had a tough road in this part of the state in the primary, where voters picked New York Sen. Hillary Rodham Clinton by a 3-to-1 margin. Even those who turned out to hear him speak before the Society of Irish Women in March said he seemed disconnected from the middle-class and unable to represent their interests. Others there said they couldn't support a candidate so young and so inexperienced with foreign policy.

Mr. Biden brings to the ticket everything Mr. Obama is lacking, said supporters gathered yesterday at Cosgrove's pub for a party celebrating the vice presidential selection.

"He's experienced. He's one of the most intelligent men I ever heard speak. He can talk to normal people," said Jack Evans, 48, president of the Lackawana County AFSCME union, which endorsed Mrs. Clinton in the primary but now backs Mr. Obama.

Supporters said Mr. Biden understood both economic and personal struggle, having lost his wife and young daughter in a car accident and suffered two brain aneurysms that nearly killed him.

Often referred to as "Pennsylvania's third senator," Mr. Biden lived in Scranton until age 10 and returned nearly every summer of his childhood and often on adulthood.

That doesn't much matter to Pat Champion, a retired letter carrier and Clinton supporter from nearby Clark's Summit.

"I don't care whether he came from Pennsylvania. What matters is who he is, she said while she and 100 other Scranton-area Democrats gathered around televisions at Cosgrove's to hear Mr. Biden's first speech as the presumptive vice presidential nominee.

Several in the crowd were brought to tears. Among them were longtime friends who were there they day fearless Joe Biden, at 7 or 8 years old, took a dare to run under a piece of construction equipment while it was moving. Others could point out the Scranton classroom where he spent his earliest school days, the mom-and-pop store where he spent his weekly 25-cent allowance on baseball cards, and the exact spot where he fell on a broken soda bottle, injuring his arm.

"I had a lot of flashbacks today to when Joe Biden was little and we lived across a dirt alley from each other," said a weepy James P. Kennedy, now a magisterial district justice and still a friend of the Biden family, who moved to Delaware more than 50 years ago but often return to Scranton for extended visits.

Mr. Kennedy, 68, wasn't the only one in the crowd at Cosgrove's using pub napkins to dab wet eyes as Mr. Biden's spot on the ballot was announced. Some had never even met the Delaware senator but were moved to tears anyway.

"It brings happiness to me when I see there's someone who says he's going to change everything. I know so many people have it so bad, and here is hope," said Dorothy McGuire, 74, of suburban Scranton. "I wanted to Biden to be president and I was disappointed when he withdrew , but here he is running for vice president. We can all be happy now."

It helps that Mr. Biden mentioned Scranton more than a few times in his acceptance speech on the steps of the old Illinois Capitol, she said.

"That matters a lot. He's a Scranton native and people here just love that. I think the people feel closer to Obama now because he has someone from Scranton and I hope the state feels the same way," she said.

Former Lt. Gov. Bill Scranton, of the influential Republican family for whom the city was named, isn't so sure that will matter statewide.

"It's going to help a tremendous amount in Scranton and Lackawanna County. It's going to bring a lot of folks on board who were strong Hillary [Clinton] supporters in the primary and have been reluctant Obama supporters," Mr. Scranton said in a telephone interview. "It firms up votes for him in this part of the state, but statewide and nationwide it's still going to be a race between the No. 1's. I'm not trying to minimize it. I like Joe Biden, but I don't think he wins the state for Obama unless it hinges on people in Lackawanna County who would otherwise be undecided."

That could happen, said Paul Ware, an assistant district attorney in Lackawanna County. Pennsylvania is viewed as a key battleground state, and a homegrown vice-presidential candidate could have sway.

"Scranton is typical of a lot of working-class cities" that are looking for the same qualities in presidential and vice-presidential candidates. "People here value their faith, they value their work and they value their families. Scranton is a microcosm of the rest of the country."

Foreign policy experience is what makes Mr. Biden a smart pick for vice president, said U.S. Sen Bob Casey, the Scrantonian who hosted yesterday's party at Cosgrove's. He said it diffuses arguments by Arizona Sen. John McCain, the presumptive Republican nominee, who has made foreign policy a central campaign issue.

"This is a fine choice. It was my preference for a long time," said Mr. Casey, a longtime friend of Mr. Biden.

"Joe Biden understands the economic hardships because of his own life story. ... He is someone who has never forgotten where he's come from -- not only in a geographic sense, but he understands his roots."

He grew up in a working-class family where his father fixed boilers, sold cars and, during lean times, moved his family into his in-laws' house. In introducing him to voters yesterday, Mr. Obama referred to him as "that scrappy kid from Scranton" and Mr. Biden referred to himself as "an Irish Catholic kid who grew up in Scranton."

On cue, the 100 people gathered at Cosgrove's whooped and hollered at every mention of their hometown.

"He has a clear connection with Scranton that will not be broken," Mr. Scranton said. "In terms of ability to speak to the lunch-pail, blue-collar American, obviously, he's got some credentials."