* Romney makes up ground on host of issues - Reuters/Ipsos polling
* Obama expected to be more aggressive in second encounter
* Libya, abortion, among issues that could come up on Tuesday
By John Whitesides
WASHINGTON, Oct 14 (Reuters) - Losing ground to Republican Mitt Romney on a host of issues, President Barack Obama faces a serious challenge to put his re-election bid back on track when the two men face off on Tuesday in their second debate.
Obama's passive performance in their first debate two weeks ago and Romney's subsequent surge have raised expectations for a more fiery encounter at New York's Hofstra University.
The Democratic president's team has been encouraged by the feisty performance of Vice President Joe Biden last week in his debate against Republican vice presidential nominee Paul Ryan.
Now, with Romney having virtually erased Obama's lead in national polls just three weeks before the Nov. 6 election, Obama is hoping to take advantage of the town hall-style format in Tuesday's debate to make a direct pitch to voters.
Obama is likely to pitch his economic vision, which focuses on a tax breaks for the middle class and tax increases for the wealthy. Romney has called for across-the-board tax cuts and sparred with Obama over whether such a plan would add to the nation's debt problems.
On Sunday, Reuters/Ipsos surveys of likely voters indicated Romney had closed the gap or overtaken Obama in the past two weeks on a range of issues - from who would be better at creating jobs to dealing with taxes and Iran's nuclear ambitions.
Although the U.S. unemployment rate dipped below 8 percent last month for the first time since Obama took office in January 2009, Romney now leads the incumbent by 42.5 percent to 39.2 percent among likely voters on the question of who would be better at creating jobs. That reverses a lead of almost 6 points for Obama on that issue on Sept. 30, before the first debate.
The pressure is now on Obama, who has acknowledged he was "too polite" in that debate, to be more confrontational without appearing strident or desperate. For Romney, the task is simply to turn in another sure-footed performance that keeps the Republican momentum rolling.
"Obama can't afford another really bad debate performance, he won't have time to recover," said Bruce Buchanan, a political scientist at the University of Texas. "He's up against it now."
Biden showed his boss the way on Thursday with an energetic debate against Ryan. Both sides seemed happy after that debate, but most polls indicated that more voters saw Biden as the winner, despite criticism of his sarcastic asides, dismissive grins and questions over his claim that the administration was not fully aware of the security needs at the U.S. consulate in Benghazi, Libya, before an assault there last month that killed U.S. Ambassador Chris Stevens.
To fire up Democrats while retaining the sympathy of independent voters who like him personally but are uncertain about his leadership, Obama will have to show Biden's passion without his histrionics.
Obama often displays that passion on the campaign trail, comfortably hammering Romney with an easy style. Whether he can do so in the town-hall format of the debate, where undecided voters will ask questions of the two candidates, is an open question.
The intimate setting of that format sometimes restrains candidates from being too aggressive as they focus on questions from individuals rather than a moderator.
"You don't want to be too nasty in front of those voters, you need to have to have your empathy antenna up," said Dante Scala, a political scientist at the University of New Hampshire.
But the change in atmosphere from a stilted one-on-one standoff could make Obama "feel more at liberty to be expressive, less somber," Buchanan said. "He's very good at using crowds in a jocular way to attack his opponent. He does that every day on the stump."
ROMNEY'S POLL SURGE
A Reuters/Ipsos daily online tracking poll on Sunday showed Obama leading Romney by 1 percentage point, 46 to 45, down from a 3-point Romney lead last Thursday - a possible sign that the Republican's surge after the first debate could be running out of steam.
But underlying trends in Reuters/Ipsos data are worrying for Obama. They show voters are evaluating Romney more favorably on key issues that could influence how they vote.
The Reuters/Ipsos online data showed that Obama is now behind on who has the better plan for the federal deficit. Obama was ahead by 1 point two weeks ago; Romney now has a significant lead on that issue, 43.4 percent to 29.9.
The former Massachusetts governor has overtaken Obama on who has the best plan for the economy, and now leads on that question by 43 percent to 37.6. Answers to the issues questions have a credibility interval - a way of measuring the accuracy of polls - of around 2.5 percent for each number and are based on samples of 1,700 respondents.
Perhaps because of Republicans' questions over how the Obama administration has handled the Benghazi attack, Romney has even crept up on issues long seen as safe territory for Obama, such as the war on terrorism and dealing with Iran.
The president's lead on Iran has shrunk from nine points two weeks ago to less than one and from 11 points to three on the war against terrorism.
On domestic economic issues, the Reuters/Ipsos data showed that Romney - a former private equity executive who has been battered for months by pro-Obama ads casting the Republican as an insensitive job-killer - has carved into Obama's lead on issues such as taxes and Social Security policy. The president now leads on taxes by 41.5 percent to 39.1, and by 40.9 percent to 37 on Social Security.
Polls also show Romney gaining ground in key swing states that could decide the election, although Obama has retained a slight lead in the vital battleground state of Ohio. No Republican has won the White House without winning Ohio.
Obama was in Williamsburg, Virginia, on Sunday for debate preparations. He promised in a radio interview last Wednesday to confront Romney more directly on their policy differences.
"I think it's fair to say that we will see a little more activity at the next one," Obama told radio host Tom Joyner.
Romney's camp is getting ready for a much more aggressive Obama, Ohio Sen. Rob Portman said on Sunday.
"I think President Obama is going to come out swinging. I think he's going to have to compensate for a poor first debate, and I think that will be consistent with what they have been doing this whole campaign," Portman, who is helping Romney with debate preparations by playing Obama, told ABC's "This Week."
The debate on Tuesday will be followed in less than a week by the final debate, on foreign policy, on Oct. 22, giving the candidates their final chance to shift momentum in the election.
Once the last debate concludes, there will be two weeks before the election and both campaigns will be focused on voter-turnout operations designed to identify supporters and get them to the polls.
"That's the pressure that both candidates face," Scala said. "After these debates the opportunities are going to be very scarce to turn things around."
Presidential debates typically draw fewer television viewers as they go on, making it harder to shift perceptions in later debates. The first one between Obama and Romney drew an audience of 67 million viewers.
Biden's showdown with Ryan raised fresh lines of attack for both parties that are likely to come up on Tuesday, including Libya, abortion rights and Romney's comments in a secretly recorded video about the "47 percent" of Americans who he said are government-dependent victims.