"His campaign and his surrogates have made wild and reckless accusations that disgrace the office of the presidency," Romney told a rally of about 5,000 supporters Tuesday night in Chillicothe, Ohio, the last stop on a five-state bus tour.
"Another outrageous charge came a few hours ago in Virginia -- and the White House sinks a little bit lower," Romney said. "This is what an angry and desperate presidency looks like."
The presumptive Republican presidential nominee said Obama's campaign strategy was "to smash America apart and then try to cobble together 51 percent of the pieces. If an American president wins that way, we all lose."
He added, "Mr. President, take your campaign of division and anger and hate back to Chicago and let us get about rebuilding and reuniting America."
Romney's Virginia comment referred to a remark Vice President Joe Biden made Tuesday to a Danville, Va., audience some observers said appeared to be roughly half African-American.
Biden said Romney vowed, if he were president, "to let the big banks write their own rules -- unchain Wall Street," Biden said with a flourish.
Then he lowered his voice and said, "They're going to put y'all back in chains."
An Obama aide later told The New York Times the White House stood by those provocative words.
Biden defended his remarks.
"The last time these guys unshackled the economy, to use their term, they put the middle class in shackles," he said in Wytheville, Va. "That's how we got where we are. Nine million jobs lost, wage stagnation, $16 trillion in wealth you all lost, in your home equity, in your 401k's and your pension plans.
"You're the ones that got nailed. All of America except for the very few," Biden said.
"And I'm told when I made that comment earlier today in Danville, Va., the Romney campaign put out a tweet -- you know tweets [through the Twitter microblogging service] -- and went on the air, went on the airwaves, saying 'Biden's outrageous in saying that.'
"I think I said, instead of 'unshackled,' 'unchained' or -- anyway, outrageous to say that, that's what we meant. I'm using their own words," Biden said.
"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."
Romney's campaign started airing a negative TV ad in critical battleground states Tuesday that accuses Obama of raiding $716 billion from Medicare to pay for healthcare reform -- an allegation Romney asserted in his Chillicothe rally speech.
"He is taking your money to finance his risky and unproven takeover of the healthcare system," Romney said. "He is putting Medicare at greater risk. He is putting healthcare at greater risk. He is putting your jobs at greater risk. We will not let Obamacare happen."
Obama campaign spokesman Ben LaBolt said, "Gov. Romney's comments tonight seemed unhinged." He said the negative campaign ads were "demonstrably false."
The Obama campaign noted the former Massachusetts governor supports the budget of his running mate, House Budget Committee Chairman Paul Ryan, which includes the same $716 billion baseline Medicare cuts Obama uses.
"They're spending millions of dollars on a lie to try to distract from the Ryan budget because they know it's absolutely devastating for them with voters of all ages," top aide Stephanie Cutter told The Washington Post.
"Unfortunately, the fact that both Mitt Romney and Paul Ryan want to turn Medicare into a voucher and raise costs for seniors by up to $6,000 blunts everything else in this conversation," she said.
Senior Romney adviser Ed Gillespie told the Post: "Stay tuned. There's a lot more to be had here."
The campaign accusations also flared around energy policy.
Romney said at a coal-mining company earlier Tuesday he would wean the United States from energy sources outside North America if he served two terms as president.
He then questioned Obama's support of coal.
"If you don't believe in coal ... then say it," he said. "If you believe that the whole answer for our energy needs is wind and solar -- why, say that."
Obama has said he favors an "all-of-the-above" energy policy and does not oppose coal or oil drilling, He has championed alternative-energy sources such as wind and solar.
During a speech is Oskaloosa, Obama said Romney has called alternative energy sources "imaginary" and said Ryan calls them a "fad."
"During a speech a few months ago, Gov. Romney even explained his energy policy this way: 'You can't drive a car with a windmill on it,'" Obama said from a podium set in a field of windmills. "I wonder if he actually tried that. That's something I would have liked to see."
Obama added: "I don't know if he's actually tried that. I know he's had other things on his car."
The remark alluded to Romney's once having placed his dog Seamus in a crate mounted to the roof of his station wagon during a family vacation.
The Romney campaign called the remark unpresidential and said Romney was "a strong supporter of wind power" and would find ways of promoting the industry.