WASHINGTON -- Republican presidential challenger Mitt Romney charged Wednesday that President Barack Obama is running a campaign "of enmity and jealousy and anger" and called on him to lift the tone of political discourse.

In an escalation of an increasingly acrimonious campaign, Romney went on national television to say he thinks Obama is "running just to hang onto power, and I think he would do anything in his power" to remain in office.

Romney was asked about the charge from the Obama campaign that the Romney campaign has become "unhinged." "I think unhinged would have to characterize what we've seen from the president's campaign," he said.

"These personal attacks, I think, are just demeaning to the office of the White House," he added.

The campaign has been lurching toward a more intensive stage in the wake of Romney's announcement Saturday of conservative Rep. Paul Ryan of Wisconsin as his vice presidential running mate.

Even before that, independent groups supporting the respective campaigns had been running increasingly provocative TV ads, including one from a group supporting Obama. That commercial suggested Romney was personally responsible for the death from cancer of the wife of a man who worked at a steel plant that was bought and subsequently shut down by Romney's venture capital firm, Bain Capital.

The tone reached a fever pitch Tuesday in connection with a remark Vice President Joe Biden made to a mostly black audience in Danville, Va. Commenting in response to Republican criticism that the Obama administration had sought to regulate Wall Street too tightly, Biden said the GOP wanted to "unchain Wall Street."

The vice president went on to say, "They're going to put y'all back in chains."

Speaking in Wytheville, Va., later Tuesday, Biden said he had meant to use the term "unshackled." But he did not apologize, and he mocked the Romney campaign for showing outrage.

In his interview Wednesday on "CBS This Morning," Romney said, "I can't speak for anybody else, but I can say that I think the comments of the vice president were one more example of a divisive effort to keep from talking about the issues."

"The president's campaign is all about division and attack and hatred and my campaign is about getting Americans back to work and creating more unity in this country," he said.

Meanwhile, Obama's campaign is launching state-specific efforts to target elements of Ryan's austere budget proposals, expanding beyond its opposition to the Republican vice presidential candidate's Medicare overhaul.

The developing Obama strategy comes as Romney and Ryan make clear they plan to campaign aggressively on Medicare, not run away from it. In person and in a television ad, the Republicans argued Tuesday that Obama is the one who cut spending for Medicare to put money toward his divisive health care overhaul.

Obama was campaigning in Iowa on Wednesday, the final day of his three-day bus trip through the Midwestern swing state. First lady Michelle Obama was joining the president, marking their first joint appearance on the campaign trail since May. Romney had a pair of private fundraisers in North Carolina and Alabama.

In states with large military and veteran populations - Florida, Ohio and Virginia among them - the Obama campaign plans to attack Ryan's proposed cuts for veterans' benefits and care, a campaign official said. The official was not authorized to discuss the campaign strategy publicly and requested anonymity.

In Colorado, Ohio and Iowa, the campaign sees opportunities to capitalize on Ryan's proposed cuts to clean energy industries that are taking hold in those states. The Obama team will argue that cutting those investments would essentially cede new energy technologies - and the jobs that could come with them - to countries like China, the official said.

In Nevada and several other states, the campaign plans to push the impact of Ryan's budget on education, citing estimates that it would cut 200,000 children a year from Head Start, an early education program, and reduce Pell grants for 10 million college students.

The campaign launched an ad Tuesday in five states - Colorado, Iowa, Nevada, Ohio and Virginia - that links Romney directly to the Ryan budget's impact on college grants.

Obama's team may launch other paid advertising on elements of Ryan's budget soon. But for now, the campaign is focused on getting its message out in local media and directly to voters through its ample grass-roots network, which still trumps Romney's ground game in some states.

Despite ramping up new areas of attack, Obama's campaign is still eager to link Romney to Ryan's Medicare proposals, both on the national level and in battleground states with a significant number of voters over the age of 65, including Florida, Ohio, Iowa and Pennsylvania.

The president's pollsters wrote in a campaign memo that Ryan's Medicare proposals are a "game changer" in Florida, the battleground state with the most electoral votes up for grabs in November.

Romney launched a strong Medicare counterattack Tuesday, accusing Obama of having "raided" $716 billion from the Medicare trust fund.

"And you know what he did with it? 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," Romney said at a campaign stop in Beallsville, Ohio, as he neared the end of a multistate bus trip that began with his weekend selection of a running mate.

Romney's campaign also released a commercial Tuesday containing the same allegation that began airing immediately in several battleground states, although officials declined to provide details.

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."

Obama campaign spokesman Danny Kanner criticized Ryan's answers, calling the Wisconsin congressman "not ready for prime time."

"First, he attacked the president for the very same Medicare savings that he includes in his own budget," Kanner said in a statement. "In the same breath, he falsely claimed that the Romney-Ryan budget protects Medicare - in fact, their plan would end Medicare as we know it, leaving seniors with nothing but a voucher in place of the guaranteed benefits they rely on today."

The Obama campaign released a web video Wednesday that declares Romney and Ryan "plan to end Medicare as we know it." It features news commentators and liberal analysts such as economist Paul Krugman declaring that Ryan's House Republican budget would mean millions of older Americans would be unable to afford health care.

The video declares that Romney has lied about Obama's record on Medicare, and says Obama's proposal cuts payments to Medicare providers but offers more benefits to Medicare participants.

Romney and the Republican National Committee planned to release a new Spanish language TV ad Wednesday highlighting Obama's economic policies. Romney's campaign didn't say where it would run or how much money they plan to spend on the spot.