Meet the change agent and his new friend, the personification of the status quo.
But, Barack Obama said, with a difference:
"Joe Biden is that rare mix," he told a crowd of thousands in Springfield, Ill., yesterday: "For decades, he has brought change to Washington, but Washington hasn't changed him."
It may not be the easiest ticket for some to digest, Reynolds said. But Joseph Biden brings something to the table that is invaluable to the man who will lead the Democrats into the fall.
Biden brings experience.
"All my years in the Senate, I have never in my life seen Washington so broken," he said, following Obama's introduction of him as the Democratic vice presidential pick.
A 35-year veteran of the Senate, who chairs the Foreign Relations Committee, Biden fills out the ticket's resume in ways Obama cannot.
"These times call for a total change in Washington's worldview," Biden said. "These times require more than a good soldier; they require a wise leader."
A pro-choice Catholic, he can appeal to ethnics, and at 65 could help Obama with the older voters who've proven resistant to his charms.
But Biden comes with baggage, too.
He's been in Washington since Obama was 11 years old, and has a long record of votes opponents will be scanning for potentially exploitable problems.
This year, in his second presidential run, he finished fifth in the Iowa caucuses.
And he is definitely not Hillary Clinton. How her supporters will react to such a conventional choice is an issue, though Clinton herself said Biden is an exceptionally strong choice.
John McCain's campaign reacted critically, releasing a statement raising doubts about the pick more than an hour before it was even made official, and following up with an advertisement touting Biden's previous criticism of Obama.
McCain himself kept the pressure on in an interview yesterday afternoon with Katie Couric.
"Well, I've always respected Joe Biden, but I disagreed with him from the time he voted against the first Gulf War to his position where he said you had to break Iraq up into three different counties. I never agreed with that."
But if criticism of the presidential nominee is a disqualification, that would make it tough for McCain to make Mitt Romney his sidekick (as he is rumored to be considering). Whatever they may say about each other now, Romney and McCain could barely conceal their mutual contempt during the primaries.
As for Biden, the best thing about him is that his qualifications are really beyond dispute. In fact he's so qualified some may wonder why he's number two and Obama's number one, instead of the other way around.
Joe Biden has been elected to the Senate six times, the first time at just twenty-nine years old.
Whatever criticisms they lob at his nearly two-decades-younger presidential running mate Barack Obama, you cannot call this Senator from Delaware inexperienced, notes Dozier.
But his life has been tempered by tragedy. Shortly after that election in 1972, Biden lost his first wife and a daughter in a car accident. His two sons were gravely injured.
"I didn't feel whole. I felt like a piece of me died."
The man his father called "Champ," fought his way back, rising to the highest ranks of the Senate.
Biden voted to authorize the war in Iraq, which may provide a counterpoint to Barack Obama's opposition to the war. In fact, his son will soon head for a National Guard tour of duty there.
But this oft-described master of American foreign policy is also known as a gaffe-master, including on matters of race.
"You cannot go to a 7-Eleven or a Dunkin Donuts unless you have a slight Indian accent," he once remarked.
And of course, that infamous, off-hand comment during the primaries, aimed at his now-running mate: "You've got an African American, articulate and bright and clean and a nice-looking guy."
Biden's 1988 presidential run was also derailed not by his own words but by words he admitted were borrowed, from British politician Neil Kinnock.
Yet, just as Joe Biden overcame his childhood stutter, some believe his willingness to speak his mind could now prove his greatest asset against the Republicans.
"The role of the attack dog is something he is quite comfortable with," said Julian W. Zelizer, professor of history and public affairs at Princeton University.
… Leaving Barack Obama to be the gentleman in the race.