Former Secretary of State Hillary Rodham Clinton has retained her lead on the rest of the 2016 Democratic presidential field, but Vice President Joseph R. Biden runs better than Mrs. Clinton against top Republicans, according to a poll released Tuesday.
Mrs. Clinton has the support of 45 percent of likely Democratic primary voters in the Fox News poll, followed by Sen. Bernie Sanders of Vermont at 25 percent and Mr. Biden at 19 percent.
Mr. Biden has not yet announced his 2016 plans and is not scheduled to join Mrs. Clinton, Mr. Sanders and others at the first Democratic presidential debate later Tuesday in Las Vegas.
The vice president was still the most frequently named second choice in the poll at 31 percent, followed by Mrs. Clinton at 24 percent and Mr. Sanders at 15 percent.
Among registered voters overall, Mr. Biden also fared better than Mrs. Clinton in potential head-to-head match-ups against top Republican presidential candidates, leading Sen. Marco Rubio of Florida by 1 point, retired neurosurgeon Ben Carson and former Hewlett-Packard CEO Carly Fiorina by 4 points each, former Florida Gov. Jeb Bush by 5 points, and businessman Donald Trump by 13 points.
Mrs. Clinton, meanwhile, trailed in four match-ups against Republicans. She trailed Mrs. Fiorina by 3 points, Mr. Bush by 4 points, Mr. Trump by 5 points and Mr. Carson by 11 points.
A hypothetical Democratic ticket with Mr. Biden running for president and Sen. Elizabeth Warren of Massachusetts running for vice president would beat a Trump-Fiorina ticket, 48 percent to 42 percent, according to the poll.
And a Biden-Warren ticket would beat a Bush-Rubio ticket by a 45 percent to 43 percent margin, the poll said.
Ms. Warren is not running for president, but she has met recently with Mr. Biden and is a hero among many liberals.
The survey of 1,004 registered voters was conducted Oct. 10-12 and has a margin of error of plus or minus 3 percentage points. The subgroup of 353 likely Democratic primary voters has a margin of error of plus or minus 5 percentage points.