"And you know what he did with it?" Romney said. "He's used it to pay for Obamacare, a risky, unproven, federal takeover of health care. And if I'm president of the United States, we're putting the $716 billion back."
In a campaign without summer doldrums, the rival sets of ticketmates campaigned in a half-dozen of the most hotly contested states, in settings as diverse as a coal mine in Ohio (Romney), a wind farm in Iowa (Obama) and a casino in Nevada (Ryan).
Vice President Biden sparked a campaign commotion Tuesday when he told a crowd in Virginia that Romney's banking policies would "put you all back in chains."
Campaigning in Danville, Biden told a crowd that included hundreds of black people that the Republican ticket wanted to "unchain Wall Street" by getting rid of regulations Obama signed into law two years ago.
"Romney wants to let the - he said in the first hundred days, he's going to let the big banks once again write their own rules, unchain Wall Street," Biden said. "They're going to put you all back in chains."
The Romney campaign reacted strongly to that, calling the comments "a new low" that "demonstrate yet again that the Obama campaign will say and do anything to win this election."
Biden later conceded using the wrong word, saying he should have said unshackled, but dismissed the Republican criticism. "If you want to know what's outrageous, it's their policies, and the effects of their policies on middle-class Americans."
The flurry over Biden's remarks underscored what the Obama team knows is a constant risk with the vice president - that his penchant for speaking off the cuff can sometimes result in inartful or off-color comments. Still, the Obama campaign sees Biden as one of its most valuable assets. The Scranton native has a more natural appeal to working-class voters in battleground states such as Pennsylvania and Ohio.
At a speech closing his bus tour, Romney delivered a sweeping indictment of the Obama campaign. "Mr. President, take your campaign of division and anger and hate back to Chicago," he said in Chillicothe, Ohio, insisting that Obama had abandoned his 2008 campaign's messages of hope and change.
The Obama campaign said Romney's comments seemed "unhinged."
The tempest over Biden's remark was modest compared with the building struggle over Medicare - an issue likely to play a significant role in the outcome of the election. Florida, Pennsylvania, and Iowa are among the top five states in the country in the percentage of people 65 and over, and all three are battleground states.
In a rebuttal issued shortly after the Romney TV ad was released, Obama spokeswoman Lis Smith said the president's health-care law did not "cut a single guaranteed Medicare benefit, and Mitt Romney embraced the very same savings when he promised he'd sign Paul Ryan's budget. ... The truth is that the Romney-Ryan budget would end Medicare as we know it."
Ryan, interviewed on Fox News Channel, said he and Romney believe Medicare can be a winning issue for Republicans in the fall. "Absolutely, because we're the ones who are offering a plan to save Medicare, to protect Medicare, to strengthen Medicare," he said.
Ryan didn't say so, but the budgets he has written in the House both called for leaving in place the cuts to Medicare that he is now criticizing. Romney has consistently favored restoring the funds, and his running mate said, "I joined the Romney ticket."
In Las Vegas, hundreds of protesters greeted Ryan outside the Venetian hotel as he prepared for a private meeting with mega-donor Sheldon Adelson.