United States Vice President Joe Biden came out on top of Thursday night's vice presidential debate with Republican challenger Paul Ryan, according to a Reuters/Ipsos poll.

The energetic Biden claimed a seven-point victory - 42 percent to 35 percent - among registered voters, with a similar margin among independents. Nearly a quarter of registered voters and about a third of independents were unsure who did a better job during the debate at Centre College in Danville, Kentucky.

Democrats will be hoping Biden's performance helps President Barack Obama recover from a week-long slide in the polls after his poor showing against Mitt Romney in the first presidential debate on October 3. Thursday's Reuters/Ipsos tracking poll showed Romney leading Obama 47 percent to 44 percent nationwide.

Biden, 69, interrupted Ryan, 42, on multiple occasions and spent much of the debate grinning when his opponent spoke, leading some conservative commentators to accuse Biden of being rude. But while both sides claimed victory, neither Biden's nor Ryan's favourability numbers changed considerably over the course of the debate, and Biden maintained his lead in this measure. After the debate, 54 percent of registered voters held a favourable opinion of Biden, compared to 50 percent for Ryan.

Nearly half of independents said Biden had not changed their view of him, and close to three quarters said the same for Ryan. But this was not true of all independents.

Independents did grow more favourable toward Ryan and less favourable toward Biden during the debate, but the small sample size of independents makes it difficult to draw conclusions.

Voters said Biden was more qualified to be president, as the vice president moved from 43 to 45 percent on that question over the course of the debate, and Ryan stayed at 35 percent. The Wisconsin congressman's presence on the Romney ticket may also cause trouble for the Republican Party: 27 percent of registered voters said Ryan made them less favourable toward Romney, up from 21 percent before the debate.

The online poll surveyed 629 registered voters after the debate. The credibility interval was 3.1 percentage points for polling before the debate and 4.5 percent after the debate.

- Reuters