Joe Biden and John McCain have been pals in the Senate for years, but neither pulled any punches Saturday after Biden became Barack Obama's running mate.

Biden, from Delaware, swiftly chastised the presumptive GOP presidential nominee as an out-of-touch Bush loyalist Saturday afternoon, as Obama and Biden shared the stage for the first time together as running mates at a rally in Springfield, Ill. -- where Obama launched his bid for the White House.

"I'll say straight up to you John McCain ... is genuinely a friend of mine," Biden said to the crowd. "But the harsh truth is, ladies and gentlemen, you can't change America when you boast ... (on) ‘the most important issues of our day, I've been totally in agreement and support of President Bush.' Ladies and gentlemen, that's what he said."

"You can't change America when you supported George Bush's policies 95 percent of the time."

Biden also jabbed at the Arizona senator's recent struggle answering a question on how many homes he owned.

McCain would have to "figure out which of the seven kitchen tables to sit at" when considering his own economic future, Biden said, previewing the tone for what is expected to be an unusually aggressive Democratic National Convention starting Monday in Denver.

But McCain's campaign, likewise, took aim at Biden mere hours after he was announced as Obama's running mate early Saturday morning.

The campaign quickly produced a TV ad featuring Biden's previous praise for McCain and comments critical of Obama. The ad includes footage of an ABC News debate last year, in which Biden said he stood by an earlier statement that Obama was not yet ready to be president and "the presidency is not something that lends itself to on-the-job training."

"Barack Obama sounded as though he turned over the top spot on the ticket today to his new mentor, when he introduced Joe Biden as the next president," spokesman Ben Porritt said in a statement. "The reality is that nothing has changed since Joe Biden first made his assessment that Barack Obama is not ready to lead."

Obama told the crowd gathered to see the Democratic ticket Saturday that Biden is the right mix of experience and independence.

"Today, I have come back to Springfield to tell you that I've found that leader -- a man with a distinguished record and a fundamental decency -- Joe Biden," he said. "Joe Biden is that rare mix. For decades, he has brought change to Washington, but Washington hasn't changed him."

House Speaker Nancy Pelosi also defended Biden during a press conference in Denver, saying he's an agitator in Washington who complements Obama's message of change.

There were a couple humorous stumbles during the Illinois rally. Obama referred to Biden as "the next president," and Biden introduced Obama as "Barack America."

Obama told the raucous crowd, many of whom had waited up to three hours to get their first glimpse of the Democratic duo, that he was "confident that we can take this country in a new direction, that we are ready to overcome the adversity of the last eight years, that we won't just win this election in November, we'll restore that fair shot at your dreams that is at the core of who Joe Biden and I are as people, and what America is as a nation."

Bruce Springsteen's "The Rising" blared as Biden took the stage and embraced Obama. It was their last appearance together before the convention, where Biden is scheduled to speak Wednesday.

Obama accepts the nomination on Thursday.

In an attempt to undermine Obama's expected post-convention bounce in the polls, McCain is scheduled to announce his running mate Friday at a rally in Ohio.

Obama made his long-awaited vice presidential announcement at 3 a.m. Saturday via text message to his supporters. The announcement ended days of frenzied speculation about who his vice president pick would be, with Virginia Gov. Tim Kaine and Indiana Senator Evan Bayh remaining strong contenders as late as Friday evening.

Hillary Clinton, Obama's bitter rival throughout the Democratic primaries, also had been in the running for a spot on the ticket. But she was not considered a leading candidate for the job and some of her supporters complained the timing of the 3 a.m. text message was payback to Clinton for her "3 a.m." attack ads raising doubts about Obama's experience.

Click here to read Biden's remarks in Springfield.

FOX News' Carl Cameron and The Associated Press contributed to this report.