SPRINGFIELD, Ill. -- Maybe it was the roasting heat, maybe it was the excitement of being back home in Illinois, or maybe it was the simple fact that it has been quite a while since Barack Obama served as anybody else's warm-up act. Either way, Obama nearly gave Joe Biden a sudden promotion in front of 35,000 newly minted Obama-Biden fans at the old Illinois Capitol building Saturday afternoon. After touting his running mate's experience, biography and character, Obama started to welcome Biden as "the next president of the United States" -- hastily correcting himself just before Biden appeared onstage, and introducing him as "the next vice president of the United States, Joe Biden!"

That was really the only stumble in an afternoon the Obama campaign had worked hard to set up on the eve of the Democratic National Convention. The order of the ticket restored, the veteran senator from Delaware bounded up the steps and practically ran to the podium to embrace Obama. They waved and pointed at the crowd for a few minutes, and then, as Obama sat back and listened, Biden gave the "attack dog" part of his job description an opening workout.

"Your kitchen table's like mine," Biden said. "You sit there at night, after you put the kids to bed, and you talk. You talk about what you need. You talk about how much you're worried about being able to pay the bills. But ladies and gentlemen, that's not a worry John McCain has to worry about. It's a pretty hard experience -- he'll have to figure out which of the seven kitchen tables to sit at." You could have forgotten that Biden and McCain have been friends for decades -- except that Biden brought it up, dropping references to "eight years of Bush and McCain" in the process. "He served our country with extraordinary courage, and I know he wants to do right by America," Biden said of McCain. "But the hard truth is ... you can't change America when you supported George Bush's policies 95 percent of the time."

Biden's only notable goof of the day came when he referred to Obama as "Barack America," which didn't really bother campaign aides, who have been planning a convention for the coming week that aims to send essentially that message. Obama and Biden hadn't even had a chance to sit and talk about the campaign together before they both flew into Springfield Saturday morning (Obama from Chicago, Biden from outside Wilmington, Del.) and gathered backstage briefly with their families. Obama had offered the job on Thursday afternoon, meaning that one of Washington's most talkative politicians (which is a pretty high bar) passed one of his first tests, keeping the news quiet long enough to not have the offer regretted.

Although the Obama campaign's scheme for announcing the choice by text message to its supporters was spoiled by CNN and other old-media types that weren't content to wait for word to come 160 characters at a time, aides were unruffled. Campaign manager David Plouffe told Salon that Obama's strategists had planned all along to break the news on a Saturday, even though it is typically the quietest day of the weekly news cycle. "I think everybody in America will know who we picked and why we picked him," Plouffe said. That the message went out at 3 a.m. Eastern on Saturday (around the time that major crises tend to break, if you believe Hillary Clinton's famous ad from the primary race) presumably was not planned, but forced by the media. Presumably.

The ticket came together so quietly that none of the vendors selling bootlegged Obama merchandise to the thousands of people waiting in line at the rally had managed to stock a T-shirt, a bumper sticker or even so much as a lousy button with Biden's name on it. But some members of the traveling crew that flew in from the campaign's Chicago headquarters Saturday morning were prominently displaying new gear. And by the time Obama hit the stage, the crowd had plenty of cardboard "Obama-Biden" signs to wave.

"To me, it's just kind of the culmination of lots of things for him," said Michelle Curran, 48, who lives in Springfield and came out in much colder weather for an Obama rally 19 months ago, when he announced his run in the same location. As soon as she heard about Saturday's event, she said, she knew she would come, without waiting to see who wound up on the ticket. (In fact, she didn't even sign up for the text message announcement.) "It didn't really matter. I just wanted Obama, and I knew he would make a good pick."

The pick is a culmination of many things for Biden, too. He was only 30 years old when he was sworn into the Senate (in his sons' hospital room, after a car accident that killed his first wife and their daughter and left both sons injured). The first time he ran for president, in 1988, he was younger than Obama is now. He and Obama spoke proudly of the Biden family's blue-collar, Irish Catholic roots in Scranton, Pa., and of the next generation of Bidens, including his son Beau, Delaware's attorney general, who will deploy to Iraq in the midst of the campaign this fall.

But 36 years after he arrived in the Senate, Biden is also one of Washington's senior statesmen, a respected source of institutional wisdom and, on the surface at least, he does not exactly underscore the message of change on which Obama has campaigned. The GOP has moved quickly to press that point, as well as the fact that Biden attacked Obama for inexperience throughout the Democratic primary race. "It's going to become more and more apparent to voters that the experience and knowledge needed to be president is not at the top of the [Democratic] ticket," commented one Republican operative.

On Saturday, Obama and Biden emphasized the message that will be at the heart of their campaign -- chaining McCain to President Bush -- in the final sprint for the White House. "We know what we're going to get from the other side. Four more years of the same out-of-touch policies that created an economic disaster at home and a disastrous foreign policy abroad," Obama said. "We can't afford more of the same. I am running for president because that's a future that I don't accept for my daughters, and I don't accept it for your children. It's time for the change that the American people need."

According to polls taken over the past month, Obama may need more help than he was expecting to beat McCain and bring that change -- but if Saturday afternoon was any guide, an energized Joe Biden could be the help he has been waiting for.