By Patricia Zengerle

WASHINGTON (Reuters) - Joe Biden's spirited performance in the vice presidential debate had Republicans criticizing him for snide grins and a comment on Libya, but it set the stage for President Barack Obama to try to regain his footing during a rematch with challenger Mitt Romney next Tuesday.

After Obama was seen as largely passive against resurgent Republican Romney last week in their first debate before the November 6 election, Biden fired up Democrats in Thursday's vice presidential debate by aggressively challenging Paul Ryan, Romney's running mate, on taxes, healthcare and foreign policy.

Polls showed voters saw the debate largely as a draw.

Greg Valliere, who analyzes politics for investors at Potomac Research Group, said he thought Ryan "won on points," but that Biden energized the Democrats and stopped the slide.

"This entertaining debate was all about Biden, who easily cleared a low bar," Valliere said in a note to clients on Friday.

In a sign the race is tightening again, Romney led Obama by 1 percentage point, 46 to 45 percent, among likely voters in the Reuters/Ipsos daily online tracking poll released on Friday. Romney led by 3 percentage points in Thursday's poll. Most poll respondents were questioned before the vice presidential debate.

Republicans tried to prevent Biden's performance from providing momentum for the Democratic ticket by criticizing the vice president's demeanor during the debate. They said Biden grinned too much and was rude to Ryan during their animated encounter.

And they made Biden's comments about security at the U.S. diplomatic compound in Benghazi, Libya, on September 11 their theme of the day, hoping to puncture Obama's credibility on foreign policy.

When asked during the debate about whether the mission had requested more security in the months leading up to the attack, Biden said, "Well, we weren't told they wanted more security again. We did not know they wanted more security again."

At a campaign rally in Richmond, Virginia, Romney accused Biden of contradicting testimony by U.S. State Department officials who said this week that the consulate had raised fears about security before the attack, which killed Ambassador Christopher Stevens and three other Americans.

"He's doubling down on denial," the former Massachusetts governor told the a cheering crowd.

Democrats dismissed the Republicans' stance as a bid to politicize a tragedy.

Biden's strong performance gave Obama a chance to stabilize his campaign after a bad week and deliver his own vigorous argument for why he deserves a second term in the White House.

ROMNEY MOMENTUM

A good showing at the presidential debate set for Tuesday at Hofstra University in Hempstead, New York, could give Obama a chance to halt Romney's rise since the two went head-to-head in Denver on October 3.

Fresh off that debate performance, Romney grabbed a small lead in many national opinion polls, reversing what had been a small but growing advantage for Obama since the Democratic convention in early September.

Obama was traveling to Williamsburg, Virginia, on Saturday to spend three days getting ready for the next debate.

Democratic U.S. Representative Chris Van Hollen, who helped Biden prepare, said he expected Obama to come out swinging during the town-hall style contest on Tuesday.

"I think the president will be more aggressive in terms of the facts. After all, in the last debate the president essentially listened as Mitt Romney reinvented himself and Mitt Romney reinvented all their proposals," Van Hollen told MSNBC.

Biden, 69, scored points against Ryan, the 42-year-old congressman from Wisconsin, with a fiery delivery that highlighted his experience in foreign policy and hit hard on domestic issues.

Ryan largely met his challenge of trying to show he was knowledgeable and presidential - and that Romney had not made a mistake in choosing him as his running mate.

The two campaigns both claimed victory after the debate.

"Most people who saw last night saw Paul Ryan as someone who had a command of the facts, had a clear, positive agenda for the future, and someone who's very serious about the serious issues that we face as (a) country," Republican advisor Ed Gillespie said on MSNBC's "Morning Joe."

Biden sharply questioned many of the Romney-Ryan team's positions, hitting Ryan hard on issues that Obama frustrated supporters by failing to contest in the first presidential debate.

Biden pounced upon Romney's tax returns, the Republican's position to let U.S. automakers go bankrupt, his proposal to let struggling homeowners lose their houses, and his dismissal of 47 percent of the American public as unproductive parasites.

The third and final presidential debate will take place on October 22 in Florida.

(Additional reporting by Susan Heavey and Matt Spetalnick in Washington,; Alina Selyukh in Columbus, Ohio,; and Steve Holland in Richmond, Virginia; Editing by Alistair Bell and Will Dunham)