Vice President Joe Biden placed the Obama campaign on the defensive when he told supporters in Virginia Tuesday that Mitt Romney and the Republicans would put them "back in chains."
The remark came as he accused Romney of wanting to loosen federal oversight of Wall Street.
"Unchain Wall Street," Biden said, adding, "They're going to put y'all back in chains."
Biden was speaking at a campaign event at the Institute for Advanced Learning and Research in Danville, Va., a city that is about 48 percent black, according to 2011 census numbers. The audience of about 800 reflected the area's demography, NBC News reported.
Romney spokeswoman Andrea Saul seized the moment, describing Biden's comments as "not acceptable in our political discourse" and a "new low."
An Obama campaign official said Biden was using "a derivative" of a metaphor he often uses about the need to "unshackle" the middle class. Biden followed up in his own defense during a campaign stop in Wytheville, Va.
"I'm using their own words!" he said, insisting that his "unchaining" reference was borrowed from Republican rhetoric, which describes the "unshackling" of economic forces, NBC News reported.
Though he did concede that his choice of "unchain" was more charged than "unshackle," he quickly moved onto the offensive, suggesting that the Republican backlash was outrageous.
"I got a message for them," he said. "If you want to know what's outrageous, it's their policies, and the effects of their policies on middle class America. That's what's outrageous."
Biden's response capped a day of frantic campaigning that had four candidates stumping in four battleground states.
Romney was in Ohio coal country, where he accused Obama of lying to voters about adding coal industry jobs and promised to make America free of dependence on foreign energy sources.
Obama was in Iowa, ridiculing Romney’s opposition to tax breaks for wind-energy production.
Not coincidentally, wind energy is a growing industry where Obama spoke, in rural Oskaloosa.
The president pointed out that Romney once dismissed wind power by saying "you can't drive a car with a windmill on it." Obama told his audience: “If he wants to learn something about wind, all he's got to do is pay attention to what you've been doing here in Iowa.”
Obama, as his aides had predicted, let up -- temporarily, at least -- on Romney's choice for a running mate, Rep. Paul Ryan of WIsconsin. Obama's only remarks about Ryan was to label him as "the ideological leader of the Republicans in Congress and a spokesman for Gov. Romney’s view."
His campaign took a similar tack. It began running a television ad linking Romney to Ryan's proposed budget plan, which proposes cuts to financial aid for college students, the Associated Press reported. The ad does not mention Ryan by name.
Ryan, meanwhile, appeared at a high school gym in Lakewood, Colo., where he criticized Obama for running a negative campaign.
"We've gone from hope and change to attack and blame," Ryan said.