Republican presidential candidate and former Massachusetts Gov. Mitt Romney speaks to reporters aboard his campaign plane before taking off on August 2, 2012 in Centennial, Colorado. (Photo by Justin Sullivan/Getty Images)

WASHINGTON (AP) — Republican presidential challenger Mitt Romney said President Barack Obama is running a campaign “of enmity and jealousy and anger” and called on him Wednesday to lift the tone of political discourse.

In a close and increasingly acrimonious race, 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.

He was interviewed on “CBS This Morning” from the battleground state of Ohio, one of less than 10 key states that will help decide the November election.

The race, in which Obama holds a slim lead according to recent polls, has seen more heated exchanges since Romney announced his vice presidential running mate, conservative Rep. Paul Ryan. The pick has seemed to energize both campaign crowds and the Republican Party’s base, which has been wary of Romney’s more moderate positions in the past as Massachusetts governor.

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

On Tuesday, Vice President Joe Biden told a mostly black audience in Virginia that Republicans seeking less regulation of the financial industry wanted to “unchain Wall Street.”

Biden went on to say, “They’re going to put y’all back in chains.”

Speaking later Tuesday, Bidcn said he had meant to use the term “unshackled.” But he did not apologize, and he mocked the Romney campaign for showing outrage at his remark.

In Wednesday’s interview, 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.”

Obama’s campaign on Wednesday was launching state-specific efforts to target elements of Ryan’s austere, small-government budget proposals, including an overhaul of the federal health insurance program for older Americans, or Medicare.

Romney and Ryan make clear they plan to campaign aggressively on Medicare. 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 there. First lady Michelle Obama was joining the president, marking their first joint appearance on the campaign trail since May. Romney had private fundraisers in North Carolina and Alabama.

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Associated Press writers Kasie Hunt in Columbus, Ohio, and Julie Pace and Jim Kuhnhenn in Washington contributed to this report.

Copyright 2012 The Associated Press.