Vermont 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) has strengthened his grip on the liberal base but there is growing interest on the left in 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, according to a new survey of progressive activists.

The survey from the liberal group Democracy for America (DFA), which counted votes from 96,641 of its members, finds Sanders with a comfortable lead over the Democratic presidential primary field at 42.3 percent support. That’s up from 36.2 percent in the same survey from December.

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.) is in second place at 10.5 percent, up from 7.9 percent in the previous poll.

ADVERTISEMENT

Buttigieg is by far the biggest gainer, coming out of nowhere for a third place showing with 9.7 percent support.

His meteoric rise has caught the attention of Washington insiders and establishment Democrats. But Buttigieg’s strength among grass-roots liberals in the poll could be a sign that his campaign has staying power. Buttigieg has also seen a rise in the polls in early voting states, such as Iowa and New Hampshire.

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 and former Rep. Beto O’Rourke (Texas) saw their support plunge in the survey.

Biden, who is expected to enter the race this week, is in fourth place at 7.9 percent, down from 14.9 percent in the previous survey. The former vice president has scores of influential Democratic allies and donors waiting on the sidelines to support him, but his entrance into the race sets the stage for a brutal battle between progressives and mainstream Democrats over the future direction of the party.

O’Rourke is in seventh place at 3.5 percent, down from 12.3 percent in the December poll. The former Texas congressman entered the race with high expectations after nearly toppling Sen. Ted Cruz Rafael (Ted) Edward CruzCruz blocks amended resolution honoring Ginsburg over language about her dying wish Trump argues full Supreme Court needed to settle potential election disputes Press: Notorious RBG vs Notorious GOP MORE (R-Texas) last year, but he’s seen much of his momentum blunted by the rise of Buttigieg, who is similarly pitching generational change.

“While these new poll results show Bernie Sanders retaining and even strengthening his support among progressives, the big shifts in support for the broad field of candidate we’ve seen over the last three months make it clear that Democracy for America members are very open to changing their minds, discovering new candidates, and reevaluating potential nominees based on the campaign they run in the months ahead,” said Charles Chamberlain, the chairman for DFA.

The DFA survey also found surprising support for former Alaska Sen. Mike Gravel, at 6.3 percent, and tech entrepreneur Andrew Yang Andrew YangDoctor who allegedly assaulted Evelyn Yang arrested on federal charges The Hill's Campaign Report: Biden weighs in on police shootings | Who's moderating the debates | Trump trails in post-convention polls Buttigieg launches his own podcast MORE, at 2.7 percent.

Nationally, Gravel clocks in just behind Sen. Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (D-Calif.), who is at 6.8 percent. He has nearly twice the support of O’Rourke and is in fourth place among Iowa’s DFA members, with 7.6 percent support, ahead of Biden.

“While Mayor Buttigieg was the top ‘surprise’ candidate … the enthusiastic response that the largely internet-­based campaigns of former Congressman Mike Gravel and entrepreneur Andrew Yang received in our poll were also notable,” DFA wrote in its analysis.

“It would be foolish for Democrats or the media to ignore the genuine interest our poll shows the grassroots have in their campaigns and, most importantly, the big ideas that fuel them like ending all wars and universal basic income.”

Sanders holds commanding leads across the board in the early voting states.

Sanders leads in Iowa with 43.8 percent support, followed by Buttigieg at 10.2 percent, Warren at 9.9 percent, Gravel at 7.6 percent and Biden at 6.2 percent.

In New Hampshire, Sanders is at 42.3 percent, followed by Buttigieg at 9.3 percent, Harris at 8.4 percent, Biden at 7.9 percent and Warren at 7.5 percent.

Sanders scores highest in Nevada, with 45.9 percent support, followed by Buttigieg at 9.3 percent, Warren at 8.6 percent, Harris at 8.2 percent and Biden at 7.5 percent.

In South Carolina, Sanders is at 41.3 percent support, followed by Buttigieg at 12 percent, Biden at 10.7 percent, Warren at 8.9 percent and Harris at 4.9 percent.

The DFA member survey was conducted April 1-19.