* Seeking to mobilize young voters
* "At any given time, something screws up"
* Romney preparing for final debate
President Barack Obama joked that his vice president looked good in a swimsuit and said screw-ups can happen in government as he discussed the Libya controversy, mixing comedy and serious issues in an appearance on "The Daily Show with Jon Stewart."
In a appeal to young voters, Obama largely played it straight in his sixth appearance on the liberal-leaning comedy show, which enjoys a broad following among younger viewers.
He touted the steps he had taken to lower college costs and expand rights for gays and lesbians and warned that Republican rival Mitt Romney would bring back economic policies that would favor the very wealthy over everyone else if he won the Nov. 6 election.
"Here's what I will say to everybody who's watching: The stakes on this could not be bigger," Obama said. "There's no excuse not to vote."
Voters under age 30 made up a crucial part of Obama's winning coalition in 2008, and Reuters/Ipsos polling data indicates they back him again this year by wide margins.
Younger Americans voted in near-record levels in the 2008, but it is unclear whether they will turn out again in such numbers this year. Obama's campaign has harnessed social media and set up an extensive network of on-campus volunteers to help ensure young supporters vote this year, and an appearance on "The Daily Show" is likely to help.
With an average audience of 1.1 million, the Comedy Central cable network show reaches roughly one-third of the viewership of the most popular late-night talk show, NBC's "Tonight Show with Jay Leno," according to Nielsen data provided by Horizon Media.
But it ranks first among viewers under the age of 50, according to figures provided by the show.
Obama promised viewers he would keep working to help the economy recover from the deepest recession since the 1930s, but he also emphasized issues like student loans and civil liberties that are normally not a central part of his stump speech. He said he still wanted to close the Guantanamo Bay military prison for terrorism suspects, which he has been unable to do so far.
Asked about the administration's shifting assessment of last month's deadly attacks on a U.S. diplomatic mission in Libya, Obama said his administration was still piecing together the evidence.
"The government is a big operation. At any given time, something screws up and you make sure you find out what's broken and you fix it," he said.
The edgy humor that Stewart is known for surfaced occasionally.
"How many times a week does Biden show up in a wet bathing suit to a meeting?" Stewart asked in an unprompted reference to Vice President Joe Biden.
"I had to put out a presidential directive on that. We had to stop that," Obama said. "I gotta say, though, he looks pretty good."
At another point, when Obama said some of his proposed legal reforms were not "sexy," Stewart stopped him.
"You don't know what I find sexy," Stewart said.
Obama nearly took the bait, mentioning that the erotic bestseller "Fifty Shades of Grey" had come up in an earlier segment of the show. Then he appeared to catch himself.
"We're not going to go there, Jon. I'm still the president," he said.
The Democratic incumbent has rebounded since a sharp debate performance on Tuesday night in which he was widely judged to have gotten the better of Romney.
A Reuters/Ipsos daily tracking poll showed Obama holding a slight but steady lead, with 47 percent of likely voters saying they planned to vote for Obama, compared with 44 percent for Romney.
Other polls show a tighter race, and the focus is on swing states like Ohio and Florida that will likely decide the election. The Romney campaign said it was moving resources out of North Carolina, where it sees an increasing chance of winning, to allocate them to other battleground states. The campaign said its communications director for the state was redeploying to Ohio.
Romney's economic plans have "resonated strongly" in the Southern state and polls are increasingly widening, spokeswoman Sarah Pompei said.
The two men face off in their last debate on Monday in Florida, where the topic will be foreign policy.
They will meet before then in New York on Thursday night, where they are expected to deliver humorous remarks at a political dinner.
Romney spent the day at a Manhattan hotel preparing for the debate and his evening speech.