Vice President Joe Biden inadvertently tossed raw meat to Republican rivals Tuesday barely 24 hours ahead of the first presidential debate, saying the middle class has been "buried" during the last four years.
With President Barack Obama and Republican nominee Mitt Romney laying low ahead of Wednesday's Denver showdown, their running mates battled for the spotlight, and Republicans suggested Biden's gaffe marked a stunning admission five weeks away from the November 6 election.
"How they can justify raising taxes on the middle class that's been buried in the last four years," Biden, addressing supporters in North Carolina, said in reference to the period he and Obama have been leading the nation.
The White House quickly sought to douse the flames, saying Biden was talking about how president George W. Bush's policies continued to hurt the middle class deep into Obama's term.
And Biden himself offered up his own correction in a tweet from his official Twitter feed: "'The middle class was buried by the policies that Romney and Ryan have supported."
But the Republicans, who argue that the middle class has been hard hit by four years of an Obama economy, let fly in the blink of an eye.
"Agree with @JoeBiden, the middle class has been buried the last 4 years, which is why we need a change in November," said a tweet from Mitt Romney's official Twitter account.
Romney's running mate Paul Ryan issued a scathing response.
"Unemployment has been above eight percent for 43 months. Our economy is limping along right now. Vice President Biden, just today, said that the middle class, over the last four years, has been 'buried.' We agree," he told a rally in Iowa.
"That means we need to stop digging by electing Mitt Romney the next president of the United States."
Republicans suggested it would be an easy punchline for Romney during Wednesday's prime-time debate.
"Thank you Vice President Biden," former New Hampshire governor John Sununu, an aggressive Romney surrogate, quipped to reporters.
Meanwhile the election protagonists were making final preparations for perhaps the high-profile moment of the 2012 campaign: a prime-time debate watched by tens of millions which could help determine the political future of the two rivals.
Obama will aim to maintain the aura of capable commander-in-chief who has steered America away from depression; Romney will strive to knock him off his pedestal on foreign policy and blame him for the stagnant economy.
The Republican challenger spent the day with top aides and Ohio Senator Rob Portman, who is playing Obama in mock debates. When the nominee ducked out for lunch at a Denver restaurant, reporters asked if he was ready.
"I'm getting there," Romney said.
Obama too took a break from debate camp to tour the Hoover Dam, the vast concrete bulk on the Colorado River that is a symbol of public works projects undertaken in the aftermath of the 1930s Great Depression.
"It's spectacular and I've never seen it before," Obama said, although he ignored questions shouted to him by reporters about how his debate practice was going.
Obama on Sunday downplayed his own debating skills, and said the clash should not be about who could fire off the best "zingers."
Romney, a multimillionaire investor and former governor of Massachusetts, offered a similar message, saying people should not focus on "who's going to score the punches," but on substance.
When he was not mocking Biden, Ryan was outlining the importance of the coming election.
"We are picking what kind of country we're going to be and what kind of people we're going to be for an entire generation. That's the stakes in this election," Ryan told supporters in the town of Clinton, Iowa.
"Do we want stagnation or growth? Do we want dependency or opportunity and upward mobility?"
Obama currently leads the national race by five points in the latest Gallup daily tracking poll and in most key battlegrounds.
A Washington Post-ABC News poll out Monday gave Obama a slimmer 49 to 47 percent lead, but, tellingly, likely voters in swing states sided with the president by 52 to 41 percent.
And a CNN poll out on Tuesday showed Romney in a deep hole with Hispanic voters, who make up the country's largest ethnic minority demographic but who support Obama 70-26 percent.
Perhaps as an effort to woo Latinos, Romney outlined a shift on immigration Tuesday, saying he would not deport young, law-abiding illegal immigrants permitted to stay in the country under an executive order issued by Obama.
"The people who have received the special visa that the president has put in place, which is a two-year visa, should expect that the visa would continue to be valid," Romney told the Denver Post.