A national poll released Monday showed Bernie Sanders leading the 2020 Democratic presidential field.

The new Emerson survey marks the first time the Vermont senator has come out ahead of former Vice President Joe Biden in a major survey.

Emerson's poll put Sanders in first place with 29 percent support, Biden in second with 24 percent, and South Bend, Indiana, Mayor Pete Buttigieg in third with nine percent.

Biden is expected to officially declare his candidacy later this month. Buttigieg launched his presidential campaign on Sunday.

According to Real Clear Politics, Biden led every 2020 Democratic primary survey going back to October by an average of 9.5 percent.

"Biden has seen his support drop," Spencer Kimball, director of Emerson Polling, said in a statement. "In February, he led Sanders 27 percent to 17 percent, and in March the two were tied at 26 percent. Now, Sanders has a 5 point lead, 29 percent to 24 percent."

"[W]hile still early in the nominating process," Kimball added, "it looks like Mayor Pete is the candidate capturing voters' imagination; the numbers had him at 0 percent in mid-February, three percent in March, and now at nine percent in April."

The survey comes nearly two weeks after the Sanders' campaign announced it raised raised $18.2 million from nearly 900,000 individual donations in just 41 days. The average donation was $20, according to Sanders' campaign manager Faiz Shakir.

While Sanders has trailed Biden overall in nearly every major poll over the past several months, recent surveys have found the senator is leading the crowded 2020 pack among young voters and Hispanic voters—both key components of the progressive base.