DAVENPORT, Iowa -- President Obama took the stage here after the local congressman, who marveled at "one heckuva crowd" and ended many of his sentences with "folks." Like a headliner showing a warm-up act how it's done, Obama let it fly.
Mitt Romney, he said, is "doing everything he can to make sure that you don't notice what he's been saying. And we've come up with a name for this condition. It’s called "Romnesia."
"If you sit on stage in a nationally televised debate saying how much you love cars -- you're a car guy -- except you wrote an article titled 'Let Detroit Go Bankrupt,' then you almost certainly have 'Romnesia,'" he said, as the crowd cheered.
"If you can’t seem to remember the policies on your own website," he said, "or the promises you made six days ago, you probably have 'Romnesia.'"
Most campaigns go negative; the Obama campaign has gone sarcastic.
Obama has unleashed a stream of jokes at his opponent's expense, with an ever-sharpening edge, since he lulled tens of millions of Americans with his academic-ese in his first debate and jeopardized his reelection.
The candidate who once dissed his opponent for working up zingers before debates has become the King of Zing.
Team Romney calls it desperation. If "the president feels the need to play Scrabble with his opponent's last name," press secretary Kevin Madden said, then that's "really telling about the state of his closing argument."
The reproach doesn't worry the Obama camp. A president has to be assertive, senior advisor David Axelrod told reporters this week, and that’s what Obama was in his final meet-up with Romney.
A small YouGov flash poll done after the debate found Obama to be the winner but also rated him as a tad aggressive on a night when some of his most direct shots were punch lines. Overall, though, Obama's ratings from the debate were positive and his "likability" numbers are still high.
Even in the more polite battleground states, voters can handle barbed attacks, said David Yepsen, a former Des Moines Register political columnist who now directs the Paul Simon Public Policy Institute at Southern Illinois University.
"We're in a presidential campaign, and people expect a little rough and tumble," he said. "People who are turned off by Obama aren't going to be any more turned off, and a funny joke or one-liner might actually punch a message through to an undecided or wavering voter."
For his part, Romney plays it pretty straight on the trail. His jokes are of the mild sort, evocative of 1950s-style, "Leave It to Beaver" humor that sometimes makes his own aides cringe. Although Romney has shown flashes of a more biting wit, that is a side of himself he reserves for close friends and aides.
For a long time, Democrats complained that Obama wouldn't go negative at all and begged him to take off the gloves.
After his studious performance in the first debate, he did.
That's when "Big Bird" made his appearance in Obama's stump speech. In explaining how he would reduce the deficit, Romney said he would cut government spending, including public broadcasting and its iconic yellow Muppet.
"Elmo, you better make a run for it!" Obama shouted at one rally.
By the final debate earlier this week, the president was in high form.
Romney, warning of excessive defense cuts, noted that the Navy is smaller than at any time since 1917. Admirals have 28 fewer ships than some believe are necessary, he said.
"Well, Governor,” Obama said, "we also have fewer horses and bayonets ... because the nature of our military’s changed. We have these things called aircraft carriers, where planes land on them. We have these ships that go underwater, nuclear submarines."
By the metrics of social media, it was the most memorable line of the night.
Michael A. Memoli and Maeve Reston contributed to this report.