Republican challenger Mitt Romney has extended his lead over President Barack Obama to 3 percentage points, according to a Reuters/Ipsos tracking poll released Thursday before the debate between their running mates.

Romney now leads the president by 47 percent to 44 percent among likely voters in the online poll, with less than a month before the election. The Republican had a one-point lead over Obama in survey results on Wednesday, his first in more than a month.

Romney has been enjoying one of his best runs of the campaign after handily winning the first presidential debate last week, partially due to Obama's passive performance in that contest.

"The momentum is in Romney's direction right now," Ipsos pollster Julia Clark said.

Clark said Romney's rise in the poll comes from convincing undecided voters, not winning over Obama supporters. And there were signs that a large number of votes are still up for grabs.

Sixteen percent of registered voters said they could still change their minds, including 28 percent of independents surveyed.

Seven percent of registered voters said they had already taken advantage of programs that allowed them to cast their ballots early, and an additional 27 percent said they planned to vote before Election Day.

The online survey of 1,092 likely voters and 1,312 registered voters was conducted between October 7 and 11. The precision of the Reuters/Ipsos online polls is measured using a credibility interval. In this case, the poll has a credibility interval of plus or minus 3.1 percentage points for registered voters and 3.4 for likely voters.

The Reuters/Ispsos database is now public and searchable here: tinyurl.com/reuterspoll.

In other national polls released Thursday, Romney led Obama by 49 to 46 percent in a UPI survey (a five-point gain for him) and by 48 to 47 in the latest from Gallup.