Barack Obama embarked on four days of intensive preparation for next week's showdown with Mitt Romney as he sought to capitalise on Joe Biden's dominant debate performance on Thursday night.

Biden eased the pressure on Obama in his clash with Romney's running mate Paul Ryan in Kentucky, overwhelming proceedings with a combative approach that will have lifted Democratic morale but that could risk alienating swing voters.

But there is no sign that Romney's surge since the first debate is going away. The latest national Gallup tracking poll released on Friday gave the Republican a two-point, 49-47%, lead over the president.

The second clash between Obama and Romney on Tuesday night in Long Island is now shaping up into a 90-minute contest that could decide the race for the White House.

Biden overwhelmed opponent Ryan with the kind of aggression that was lacking in Obama's disastrous debate with Romney in Denver last week. But his demeanour in the first half of the contest, which showed him laughing, smirking, talking over and interrupting as Ryan spoke, may have grated with some of the tens of millions of television viewers.

Ryan, over breakfast on Friday in Lexington, Kentucky, told reporters he felt great about his own performance and had not felt overwhelmed by Biden. "No, it was what I expected," he said.

Obama cleared his diary on Friday, apart from honouring a commitment to dinner with campaign donors, the prize in one of the Democratic party's fundraising drives.

He is devoting Saturday, Sunday and Monday almost exclusively to debate preparation for the clash in Hempstead, New York, the second of three presidential debates before election day on November 6.

His chief adviser, David Axelrod, speaking in the Spin Rooom in Danville, Kentucky, minutes after the Biden-Ryan debate ended, said: "The president is looking forward to meeting Governor Romney again next week."

Asked about the risk of Biden's laughter being seen as rude and irritating to independent voters, Axelrod insisted laughter was inevitable "when you are debating an opponent who is seriously evading and distorting facts. You react to that."

The Republican national committee issued a a new web video after the debate, showing clips of Biden laughing, in contrast with a serious Ryan. One of Romney's senior advisers, Ed Gillespie, on Fox television Friday, said: "I thought it was very disrespectful to the American people."

Republicans compared it to the 2000 presidential debate in which the Democratic challenger Al Gore lost voters irritated by his sighing and rolling his eyes while George Bush was talking.

The architect of the Bush victories, Karl Rove, described Biden as looking "unhinged".

Democratic congressman Chris Van Hollen, who played the part of Ryan during Biden's debate preparations, told MSNBC: "I don't think [Biden] was over the top. I thought what you saw was Joe Biden's passion for these issues."

Before the vice-presidential debate, Republicans had been eagerly anticipating that Congressman Ryan, who has a reputation for being cerebral – he is the author of a Republican House plan for bringing down the deficit – would overcome the gaffe-prone and long-winded Biden. But Ryan seemed overcome by Biden's cajoling, forceful debating style.

While Biden's performance will have cheered Democratic activists and supporters, it was not a game-changer capable alone of arresting the slide in Obama's fortunes. The consensus among US commentators was that the debate was a draw.

The US electoral map has changed dramatically in the week since the Denver debate, with Obama's poll ratings sliding and Romney now marginally ahead or at least even with the president nationally and in most of the eight swing states. The Real Clear Politics website, which averages out the daily polls, has Romney on 47% and Obama on 46% nationally. Romney is three points ahead in North Carolina and two in Florida, with Obama three points ahead in Iowa. But the two are statistically tied in Ohio, Virginia, New Hampshire, Nevada and Colorado.

Apart from Biden's facial expressions, Republicans claimed the vice-president had made a major gaffe when he denied that there had been a request by US security forces in Libya to retain or increase protection staff at the embassy and the consulates. The state department admitted at a Congressional hearing on Wednesday there had been such a request.

In the debate, Biden was adamant: "We weren't told they wanted more security there. "We did not know they wanted more security." This comes after a series of conflicting statements from the Obama administration over what happened at the Benghazi consulate attack in which US ambassador Chris Stevens and three other Americans were killed.

Former House Republican speaker Newt Gingrich, told CBS television: "Biden on Benghazi was so wrong last night. It's going to haunt them from now until the next debate."

During the Kentucky debate, Biden, talking about Iran and Syria, tried to portray the Romney-Ryan ticket as leaning towards taking the US into another conflict, one that war-weary Americans did not want. "Facts matter," he said, lecturing Ryan on the details of Iran's nuclear programme, saying it was not yet close to achieving a weapons capability.

On domestic policy, Biden pushed Ryan on plans to cut the tax bills of the wealthy, saying they did not need it, and also questioned how Ryan could get the deficit down. Biden said no one in history had managed to do this.

"Jack Kennedy lowered tax rates, increased growth," Ryan said. "Oh, now you are Jack Kennedy?" Biden asked sarcastically.

It was a refrain of the most famous vice-presidential debate quote in US political history when the Democratic nominee Lloyd Bentsen, told Dan Quayle he was "no Jack Kennedy."

At several points in the night, Biden dismissed points made by Ryan as "malarkey".

Ryan got in a hit when he got personal, noting that unemployment in Scranton, Pennsylvania – Biden's hometown – had risen. But when Ryan went on to say, "That's how things are going all across America," the vice-president interrupted. "That's not how things are going. You don't read the statistics," he said, referring to the drop in unemployment to 7.8% announced last Friday.

Biden raised the secret video in which Romney was dismissive of 47% of the population as freeloaders, a line that Obama singularly failed to bring up last week, to the dismay of Democrats. Ryan said the 47% remark was not what Romney had meant to say.

Biden may join the race for the Democratic presidential nomination in 2016, a race that could pit him against Hillary Clinton, and this performance will have helped him with the constituency that matters, Democratic activists. If Romney fails to win next month, Ryan is among potential Repbublican contenders in 2016. While Biden dominated the debate, Ryan made no gaffes and did not harm to his chances in 2016.