Registered voters who say they have a "strong liberal" ideology prefer former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE to Sen. Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE (I-Vt.) in a hypothetical 2020 matchup against President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE, according to a new poll.

The Hill-HarrisX daily poll, conducted Dec. 16-17, found that 83 percent of self-identified progressives prefer Biden, compared to 75 percent who picked Sanders. Rep. Beto O'Rourke Beto O'RourkeJimmy Carter says his son smoked pot with Willie Nelson on White House roof O'Rourke endorses Kennedy for Senate: 'A champion for the values we're most proud of' 2020 Democrats do convention Zoom call MORE (D-Texas) was the top choice for 66 percent of "strong liberal" respondents.

Biden also received greater support from Democratic respondents as a whole, receiving 76 percent of the group's share against Trump compared to the 70 percent that the Vermont senator received.

Among all voters, Biden defeated Trump 42 percent to 36 percent, outside the poll's 3.1 percent sampling margin of error. Sanders edged the president 38 percent to 37 percent, and O'Rourke lost 30 percent to 37 percent. Biden also fared best among voters who said they lean liberal or are moderate.

(The poll did not measure how other potential Democratic candidates might do in a contest with Trump.)

Name recognition is considered the predominant factor this early in the election cycle -- former Secretary of State Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE was the front runner in 2008 before losing the Democratic nomination to President Obama -- but establishing credibility and being seen as a first-tier candidate who can appeal to various demographic groups is also vitally important.

"The real thing that Democrats are going to be debating about is this issue of who is the turnout maximizing candidate for the Democrats, who is going to get the base of the party most excited versus who can appeal to more swingish voters in key states like those industrial Midwest states that the Democrats lost in 2016," Ruy Teixeira, a political analyst with the left-leaning Center for American Progress, said Friday on Hill.TV's "What America's Thinking."

With the 2020 primaries more than a year away, rival candidates can use that time to chip away at Biden's progressive bona fides. Sanders is likely to be one of Biden's toughest critics if both men decide to pursue the presidency. In 2016, Biden took a veiled swipe at the Vermont senator, saying at an economic conference that America doesn't need socialism.

"One thing that I think the Democrats did really well in the congressional elections this past cycle is that they ran a lot of people who didn't have voting records. And when you don't have a voting record, it's a lot more difficult to attack someone," Republican pollster Jim Hobart said on "What America's Thinking."

"Someone like Vice President Biden, he's got a long voting record," Hobart added. "And I think the first people who are going to take advantage of that are Democrats in the primary."

—Matthew Sheffield

Note: This article has been updated to include additional information from the poll.