A little road rage has entered the campaign trail.
The presidential race has heated to a boil since Mitt Romney chose Wisconsin Rep. Paul Ryan as his running mate last weekend, producing a series of harsh exchanges between candidates.
"Mr. President, take your campaign of division and anger and hate back to Chicago," Romney said at one point.
Presidents usually try to stay above the fray, leaving attack-dog tactics to their running mates, surrogates and negative advertising.
But President Barack Obama is digging in, assailing Romney's character and going after Ryan's budget proposals to overhaul Medicare and turn Medicaid into a state block-grant program.
"Their plan makes seniors pay more so we can get tax cuts for millionaires and billionaires," Obama said on an Iowa bus tour, even though the GOP plan wouldn't affect anyone now over 55.
Romney and Ryan are "just throwing stuff against the wall to see what sticks," Obama said. Romney called the president "angry and desperate."
Ryan, campaigning Thursday in Ohio, said the president's "campaign is based on frustration and anger."
The two campaigns even feuded over which side was more "unhinged." Obama needled Romney for putting his dog Seamus in a crate atop his station wagon on a long-ago family vacation.
Vice President Joe Biden told a racially mixed audience in Virginia that Romney and Ryan would "unchain Wall Street" by loosening regulations and "put y'all back in chains."
Romney told reporters in South Carolina Thursday that, despite suggestions by Senate Democratic Leader Harry Reid that some years he hadn't owed any federal taxes, "Every year I paid at least 13 percent."
Romney won't release more than two years of returns. He called the "fascination" over his taxes "small-minded."
Obama and Biden stayed out of the limelight Thursday, attending meetings at the White House.