Barack Obama's Harvard pedigree, soaring rhetoric and professional demeanor have helped critics paint him as an elitist. So when he stood Saturday next to his running mate, a new set of characteristics was on display: a public university graduate of modest means, a Roman Catholic who talks like regular folks.

It is true that Sen. Joe Biden Jr.'s vast foreign policy experience may help assure voters who wonder if the youthful Obama is ready to be commander in chief and may give the Democrats a voice of gravitas to challenge the Republicans' war-hero nominee.

But it was clear Saturday that equally important to Obama's decision to select Biden was the Delaware senator's affinity for the white, blue-collar Democrats who did not support Obama during the primaries and have remained wary of his candidacy.

The newly minted partners made no secret of this goal.

As they shared the stage for the first time as the Democratic ticket, they invoked Biden's native Scranton, Pa., no fewer than five times. Obama repeatedly called the 65-year-old Biden the "scrappy kid from Scranton."

It was a less than subtle plug for the small northeastern Pennsylvania town that became a touchstone for the primary campaign of Obama's chief rival. Hillary Rodham Clinton often cited her family's roots in Scranton as she used the town to symbolize how she, more than Obama, understood the travails of hard-working Americans.

With Biden, Obama hopes to acquire some Scranton cred - in the critical battleground of Pennsylvania, as well as other important states where Democrats cannot afford to lose working-class support, such as Ohio, Virginia and Florida.

"It's nice that you can get a twofer, with one of the heaviest hitters on foreign policy in the Senate and also get someone who has the capacity to reach these lunch-bucket voters," said Democratic strategist Bob Shrum, who managed John F. Kerry's campaign four years ago.

The presence of the seasoned Biden could complicate the calculation for Republican candidate John McCain, who is expected to name his running mate shortly after the Democratic national convention ends later this week in Denver.

Had Obama tapped a less experienced Democrat, such as Virginia Gov. Tim Kaine, McCain might have gone with a fresh GOP face such as Minnesota Gov. Tim Pawlenty. But some Republicans said privately that they worried Biden might too easily dominate the vice presidential debate set for October and hoped McCain would opt for a steadier hand, such as former Massachusetts Gov. Mitt Romney or former Pennsylvania Gov. Tom Ridge.

Then again, neither Romney, who has backed abortion rights in the past, nor Ridge, who supports them now, has been embraced by the GOP's social conservative base.

Democrats, however, seemed to rally around Biden as a strategically smart choice.

While the two men seem a study in contrasts - young vs. old, black vs. white, political newcomer vs. grizzled veteran, Harvard Crimson vs. Fightin' Blue Hens of the University of Delaware - Obama aides hope the Biden biography can help sell skeptical voters on the lesser known parts of Obama's story.

Obama may be known for lamenting the high price of arugula at Whole Foods, but Biden took pains Saturday to talk about Obama's difficult upbringing by a "single mom who had to struggle to support her son and her kids."

Obama aides said they were attracted to the Delaware senator's humble beginnings - and his relatively modest lifestyle. Biden has a net worth between $59,000 and $366,000, a comparatively small sum in the millionaire's club known as the Senate.

"He's still one of the poorest members of the Senate," said Anita Dunn, a senior adviser to Obama's campaign. "He came to Washington to do good, not to do well for himself."

Biden arrives on the ticket at a time that some of Obama's weaknesses with core Democratic voters appear to be taking a toll.

A once-healthy lead in most polls has dwindled after weeks of attack ads by McCain and the GOP portraying Obama as a celebrity out of touch with the needs of everyday people.

The weakest links in the Democratic coalition continue to be whites, Catholics and blue-collar voters, a demographic slice that would seem a tailor-made audience for Biden.

About one in 10 respondents to a Wall Street Journal/NBC poll said they would have voted for Clinton against McCain but are not backing Obama. They are mostly female, heavily Catholic, largely Democratic and largely lower income, according to GOP pollster Neil Newhouse, who conducted the survey with Democratic pollster Peter Hart.

While many Clinton supporters remain raw over the competitive primary campaign and were still hoping the New York senator would be named to the ticket, Democratic strategists predicted Biden was a safer choice than others under consideration.

"Most of those who are disappointed that Hillary Clinton was chosen will readily concede that Joe Biden is a solid choice and highly qualified -- avoiding some of the hard feelings that might have occurred if some of the lesser experienced contenders had been selected," said Geoff Garin, who was a top strategist for Clinton's campaign.

Democratic strategists believe that Biden could help reframe the narrative of the campaign by focusing attention on McCain and his ties to the unpopular President Bush, as he did with evident relish in his speech.

Many Democrats were disappointed in 2000 and 2004, when the vice presidential candidates -- Joe Lieberman and John Edwards -- were outmatched in their debates against Vice President Dick Cheney. Both Lieberman and Edwards, who were eyeing their own futures as presidential candidates, appeared reluctant to come across as as overly aggressive.

But strategists expect Biden to be a far more effective and eager attack dog -- a requirement if Obama is to appear above the fray while voters are reminded why they feel the country has been on the wrong track under GOP leadership.

"If it's a referendum on Obama, then the question is much less about how bad Bush and McCain are and about how good really is Obama," said Democratic pollster Mark Mellman. "And that's where the doubts that the Republicans have tried to create begin to seep in."

-

Times staff writers Janet Hook and Chuck Neubauer in Washington contributed to this report.