Poll: 33 percent of voters undecided on who won third Democratic debate

More people said they were uncertain about who won last week's Democratic presidential debate than picked a specific winner, according to a new Hill-HarrisX poll released on Monday.

Thirty-three percent of people said they were unsure which of the the 10 candidates on the stage won the debate, a figure more than a third higher than the 20 percent of Democratic voters who said former Vice President Joe BidenJoe BidenBiden: Democrats' spending plan is 'a bigger darn deal' than Obamacare Biden says he's open to altering, eliminating filibuster to advance voting rights Biden: Comment that DOJ should prosecute those who defy subpoenas 'not appropriate' MORE was the winner and did the best. 

Twelve percent thought that Sen. Elizabeth WarrenElizabeth WarrenDemocrats scramble to reach deal on taxes Ethics office warned officials about unnecessary trades Fed imposes tougher rules on financial trades amid scandal MORE (D-Mass.) had the best performance, and 9 percent picked Sen. Bernie SandersBernie SandersBiden says expanding Medicare to include hearing, dental and vision a 'reach' Schumer endorses democratic socialist India Walton in Buffalo mayor's race On The Money — Sussing out what Sinema wants MORE (I-Vt.).

Sen. Kamala HarrisKamala HarrisHarris stumps for McAuliffe in Virginia Biden, Harris mark 10th anniversary of MLK memorial Watch live: Biden, Harris deliver remarks at MLK Jr. Memorial anniversary MORE (D-Calif.) came in fourth place, with 7 percent saying she did the best in the poll released Monday.

Former Texas Rep. Beto O’Rourke (D) and Sen. Cory BookerCory BookerSenate Democrats call for diversity among new Federal Reserve Bank presidents Progressives push back on decision to shrink Biden's paid family leave program Emanuel to take hot seat in Senate confirmation hearing MORE (D-N.J.) tied for fifth place, with 5 percent. 

South Bend, Ind., Mayor Pete ButtigiegPete ButtigiegAirlines should give flight attendants 10 hours of rest between flights: FAA GOP memo urges lawmakers to blame White House 'grinches' for Christmas delays Emanuel to take hot seat in Senate confirmation hearing MORE, tech entrepreneur Andrew YangAndrew YangProgressive economic theories run into some inconvenient truths Andrew Yang weighs in on Dave Chappelle: Artists should get 'wide berth' for self-expression Yang says he has left Democratic Party MORE, and former Housing and Urban Development Secretary Julián Castro were the only other candidates to receive at least 2 percent of the vote or higher.

The debate was the first time the Democratic field has been contained to one stage and one night of debates.

The biggest moment of the night came when Castro, during an argument over health care with Biden, appeared to take a jab at the front-runner's age by repeatedly saying, "Are you forgetting what you said two minutes ago" to the 76-year-old former vice president.

The debate also included tough exchanges over health care, though overall the debate did not feature as many heated discussions as earlier debates.

The Hill-HarrisX poll was conducted online among 371 registered voters between Sept. 13 and 14. It has a margin of error of plus or minus 5.5 percentage points.

—Tess Bonn