Senator Bernie Sanders and U.S. Senator Elizabeth Warren shake hands before the start of the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

"If our focus is on victory, we can't be delusional about it," Mitchell told The New York Times . "You don't defeat the moderate wing of Democrats through thought pieces or pithy tweets, you defeat their politics through organizing."

The WFP is throwing its support behind Warren early in order to build a liberal coalition around a candidate to defeat former Vice President Joe Biden, the front-runner who many progressives view as too moderate.

Warren, D-Mass., released her own statement on Twitter, saying she is "grateful" for the party's endorsement in her bid to enact structural change in the country.

"Our job now is to help Senator Warren build the mass movement that will make her transformational plans a reality."

"Senator Warren strikes fear into the hearts of the robber barons who rigged the system, and offers hope to millions of working people who have been shut out of our democracy and economy," Working Families Party National Director Maurice Mitchell said in a statement.

The Working Families Party endorsed 2020 presidential candidate Sen. Elizabeth Warren on Monday. She beat fellow progressive Sen. Bernie Sanders, who won the party's endorsement in the 2016 campaign.

Warren won the endorsement with 60.91% of the vote, compared with 35.82% for runner-up Sanders. The ranked-choice poll also featured former Housing and Urban Development Secretary Julian Castro, New York City Mayor Bill de Blasio and Sen. Cory Booker, D-N.J., who were all considered after participating in a question-and-answer forum with the party's members.

The vote was carried out by the national membership and national board, which includes representatives from each state organization.

WFP's endorsement of Warren could be a blow to the Sanders campaign, which won the party's vote in 2016 over Hillary Clinton. Warren has been steadily climbing in recent polls. RealClearPolitics ranks her third among the Democratic primary candidates, with 16.8% of the vote, compared with Sanders' 17.3% and Biden's 26.8%.

The WFP has been a leading voice in the progressive movement since its founding in New York City in 1998, throwing its support behind progressive candidates across the country. It has already endorsed for the 2020 election all four members of the progressive House Democratic "squad": Reps. Alexandria Ocasio-Cortez, of New York; Ilhan Omar, of Minnesota; Ayanna Pressley, of Massachusetts, and Rashida Tlaib, of Michigan.

Sanders said of the party in 2016, "The WFP is the closest thing there is to a political party that believes in my vision of democratic socialism. The WFP shares my view of a society and an economy that works for everyone, not just the wealthy and well-connected."

Sanders' campaign manager Faiz Shakir wrote in an email: "The Bernie Sanders campaign is built from the support of millions of working people across the country, with our leading donors being Walmart workers, teachers and nurses. We look forward to working with the Working Families Party and other allies to defeat Donald Trump. Together, we'll build a movement across the country to transform our economy to finally work for the working class of this country."

The WFP endorsement could be a boon for Warren as she looks to bolster her credentials with the Democratic Party's liberal wing ahead of the 2020 primaries. Currently, Warren trails only Sanders in money raised in the campaign, according to the Center for Responsive Politics.

Warren's campaign has raised over $35 million compared with $45 million for Sanders, who leads the Democratic field in fundraising. Biden, who leads in the polls and declared his candidacy months after Sanders and Warren, has raised just over $21 million.