DENVER -- They stood as opponents on the stage at the Des Moines Register debate last December. Sen. Joseph R. Biden Jr. defended himself against a tough question on whether some of his off-the-cuff statements, including one about Sen. Barack Obama, suggested insensitivity on issues of race.
His rival stepped in.
"I have absolutely no doubt about what is in his heart and the commitment that he has made to racial equality in this country," Mr. Obama volunteered. "So I will provide some testimony, as they say in church."
On the eve of the convention where he will accept his historic nomination, Mr. Obama yesterday provided more profound testimony to his appreciation of the Delaware senator as he united their political destinies by choosing his older, more experienced colleague as his runningmate.
"Joe Biden is that rare mix -- for decades, he has brought change to Washington, but Washington hasn't changed him," Mr. Obama said as he introduced his new runningmate from the steps of the old state Capitol in Springfield, Ill. "He's an expert on foreign policy whose heart and values are rooted firmly in the middle class.
"He has stared down dictators and spoken out for America's cops and firefighters."
Like his trip to the Middle East and Europe earlier this summer, the selection of the foreign policy veteran suggests an effort to shore up a gap in Mr. Obama's own foreign policy credentials. The gamble is that he will reassure some voters about the Democratic ticket rather than reminding them that Mr. Obama is a very junior member of the Foreign Relations Committee panel that Mr. Biden chairs.
The two candidates made repeated references to Mr. Biden's Catholic, working-class roots in Scranton, demonstrating their hopes that he will be the ticket's ambassador to working-class voters. Mr. Obama lost overwhelmingly to Sen. Hillary Rodham Clinton in Scranton in the April Pennsylvania primary and was weak everywhere among the white, working class.
Within moments of jogging to Mr. Obama's side on the Springfield stage, to the strains of Bruce Springsteen's, "The Rising," Mr. Biden jumped right into vice presidential candidate's traditional role as aggressor.
While describing Sen. John McCain, the presumptive Republican nominee, as his friend, he repeatedly tied him to the Bush administration. Trying to reinforce the story Democrats had pushed all week, he said that although many Americans sit at their kitchen tables worrying over their finances, Mr. McCain would have to first figure out which of his seven kitchen tables to sit at.
"We don't have to have four more years of George Bush and John McCain," Mr. Biden said.
Later, Mr. McCain told Katie Couric on CBS News that he believes Mr. Obama picked a good man.
"Joe and I have been friends for many, many years, and we know each other very well, and so I think he's made a very wise selection. I know that Joe will campaign well for Sen. Obama, and so I think he's going to be very formidable. Obviously, Joe and I have been on different philosophical sides, but we have been -- I consider him a good friend and good man."
Mr. McCain's campaigners tried to portray the pick as one that diminished Mr. Obama. Seizing on a slip in which, before immediately correcting himself, Mr. Obama referred to Mr. Biden as "the next president," a McCain spokesman said in a statement, "Barack Obama sounded as though he turned over the top spot on the ticket today to his new mentor.... The reality is that nothing has changed since Joe Biden first made his assessment that Barack Obama is not ready to lead," said Ben Porritt, the McCain spokesman.
He referred to Mr. Biden's observation, made when he was still running against his new partner, that Mr. Obama lacked the experience to be president. Videotape of the remark was fodder for a television commercial the Republican camp had prepared within hours of the middle-of-the-night text message that announced the ticket.
Democrats appeared almost uniformly positive about the decision.
Mrs. Clinton said, "Sen. Obama has continued in the best traditions for the vice presidency by selecting an exceptionally strong, experienced leader and devoted public servant."
T.J. Rooney, the state Democratic chairman who had been a Clinton supporter during the Pennsylvania primary, said it was the best choice the nominee could have made -- with the exception of Mrs. Clinton herself. His ally, Gov. Ed Rendell, had argued even before the decision was revealed that the senator from neighboring Delaware would be Mr. Obama's best bet.
Several Pennsylvanians noted that Mr. Biden has often described himself as "Pennsylvania's third senator."
Both candidates hope that their joint venture will be more successful than either of Mr. Biden's previous attempts.
In 1988, his first presidential bid foundered when a rival campaign leaked a videotape that showed that passages of a stump speech delivered at the Iowa State Fair had been lifted nearly intact from a speech by British Labour Party leader Neil Kinnock. Mr. Biden had used the passage on other occasions but had attributed it. He ended up dropping out before the first vote was cast.
This year, he was stopped in the snows of Iowa, failing to break through to the top tier of candidates during the caucuses.
Mr. Biden joked about his long tenure yesterday -- he was first elected in 1972 at the age of 29.
While noting that only four senators had more seniority, he turned and said, "But Barack, I want you to know there's 44 older than me."
In choosing Springfield for introducing Mr. Biden, Mr. Obama was returning yesterday to the spot where he launched his then improbable presidential bid on a cold day in February 2007. Babies that weren't yet born then, Mr. Obama has often joked, are now walking and talking.
During that time, his campaign has also matured amid occasional stumbles.
That Springfield appearance was the official beginning of the campaign, but Mr. Obama's emergence as a plausible presidential candidate came with his heralded keynote address at the Democratic National Convention in Boston four years ago. The Illinois senator will figuratively echo that performance Thursday with his acceptance speech in INVESCO Field, continuing the extended process of introducing himself to American voters.
The site is symbolic of the theme of change that the campaign has sought to make its brand. The audience will include most of the Democratic Party hierarchy that will have gathered over the previous three days in the Pepsi Center.
The bulk of the crowd filling the Denver Broncos' home will comprise voters who didn't qualify for credentials for the traditional party gathering. The contrast is emblematic of the way the Obama forces have built a campaign aligned with but not dependent on traditional party structures.
Pennsylvania is an example. The Obama campaign has made its peace with the majority of state party leaders that opposed them in the spring, but its grass-roots registration and organizing efforts represent a separate if overlapping organization from the pre-existing Democratic Party structure.
The path that led Mr. Obama back to Springfield and on to INVESCO Field was unprecedented. He began as an intriguing long shot, seemingly a remote threat to Mrs. Clinton, the acknowledged front-runner. But his campaign's meticulous organization and command of new media and new voters brought him to a stunning upset in the Iowa caucuses that shattered all turnout records.
But not all of the changes since he last spoke in Springfield were as welcome. In the run-up to the Iowa showdown, where Mr. Biden was a distant also-ran, one common element among Democratic voters was that Democrats were happy with their field of candidates, and optimistic of their chances no matter which one emerged.
That amity wore thin as Mr. Obama and Mrs. Clinton battered one another through the later primaries. And the party's wide optimism that emerged from their gains in the 2006 congressional elections was tested through the summer by Mr. Obama's failure to put any real polling distance between himself and Mr. McCain.
In that nervous climate, Mr. McCain's halting accounting of his real estate holdings emerged as manna from political heaven this week, a self-inflicted rebuttal to his own campaign's effort to portray Mr. Obama as the candidate out of touch with the mores of the working class.
At the end of this week, it may be difficult to disentangle the effects of the housing exchanges, the vice presidential choice and Mr. Obama's renewed oratory on whatever polling shifts may emerge.
Anticipating the possibility of a Biden choice, a Washington Post-ABC News poll completed just before the announcement found that three-quarters of voters said picking Mr. Biden would not affect their vote. Roughly 13 percent said it would make them more likely to vote Democratic and a nearly equal proportion, 10 percent said it would make them less likely.
Rep. Jason Altmire, D-Bradford Woods, represents a southwestern Pennsylvania district that proved a tough target for Mr. Obama in the April primary.
He predicted the Biden choice would be popular with his constituents, but cautioned that voters are swayed by the top of the ticket not the No. 2.
"It's a good choice for southwestern Pennsylvania, but Sen. Obama still has some work to do," he said of his district's reaction.
That work will continue over the next four days as the Democrats officially make him the first African-American nominee in history.
Post-Gazette politics editor James O'Toole can be reached at email@example.com or 412-263-1562. First Published August 24, 2008 4:00 AM