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 has seen a surge of Democratic support in the days since he announced his 2020 presidential campaign and now sits comfortably at the top of a new survey of the race.

In the CNN–SRSS poll released early Tuesday, Biden is supported by 39 percent of the Democratic electorate, leading his nearest challenger, 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.), by 24 points. Biden and Sanders were the only candidates registering double-digit levels of support in the survey.

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The poll shows an 11-point surge for Biden since last month, when 28 percent of Democrats said they would support him in the primary.

Sanders is now supported by 15 percent of Democratic voters, according to the poll, which found Sen. Elizabeth Warren Elizabeth WarrenDimon: Wealth tax 'almost impossible to do' CNN's Don Lemon: 'Blow up the entire system' remark taken out of context Democrats shoot down talk of expanding Supreme Court MORE (D-Mass.) at 8 percent support and South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegThe Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice Hillicon Valley: FBI, DHS warn that foreign hackers will likely spread disinformation around election results | Social media platforms put muscle into National Voter Registration Day | Trump to meet with Republican state officials on tech liability shield MORE (D) with 7 percent.

Biden leads Sanders among all the major demographics, according to CNN.

Just 36 percent of Democratic votes say, however, that they are locked in to their choice for president. Biden wins the support of 50 percent of Democrats who say they have made up their minds so far, according to the poll.

The CNN–SRSS poll was conducted from April 25 to 28, and the margin of error is 5.9 percentage points for Democratic-leaning voters.

A Morning Consult survey also published early Tuesday found the vice president with the support of 36 percent of Democrats compared to 22 percent for Sanders, a 6-point surge since Biden's campaign announcement last Thursday

The Morning Consult survey, which contacted only Democratic-leaning voters, surveyed 15,475 voters with a margin of error of just 1 percentage point.