Eighteen left-wing groups, including Justice Democrats, the Working Families Party, and Sunrise Movement, signed a unity pledge this week as a response to the growing tension between Sens. Elizabeth Warren (D-MA) and Bernie Sanders (I-VT).

The groups, some of which back Sanders and others of which endorsed Warren, are urging Democrats to remain united and focus their criticisms on President Trump and “corporate” Democrats. They outlined their call to action in their “Progressive Unity Statement” released this week.

“For those with a declared preference, this statement in no way signals the slightest decrease in that commitment,” the groups said of their previous endorsements, contending that the statement is “a shared declaration of our belief that the surest way to defeat Trump is for the Democratic Party to nominate either Warren or Sanders, as these are the candidates best able to energize voters by providing a vision of a decent society and a fair economy.”

The pledge states in part:

Our best chance of defeating Trump does not lie with an establishment or corporate Democrat. The anti-establishment, anti-corporate awareness and anger that characterize American society today are justified, and it would be a huge mistake to once again yield that ground to a phony like Trump. We can do better, and will work to persuade Democrats to choose a strong, progressive nominee. Sanders and Warren, as well as their campaigns and supporters, will need to find ways to cooperate. The crossfire amplified by the media is unhelpful and does not reflect the relationship between two Senate colleagues who broadly worked well together for most of the last year. We hope to build solidarity between delegates affiliated with these two candidates prior to the convention and will encourage the campaigns to work towards a unified convention strategy after the final primaries on June 2nd.

While groups added that they believe Sanders and Warren are the candidates who should lead the country, they pledged to “go all-out to defeat Trump no matter who the Democratic nominee is” and urged other progressives to do the same.

Eighteen groups signed the pledge, including Center for Popular Democracy Action, Dream Defenders, Our Revolution, People’s Action, Progressive Democrats of America, Roots Action, and the Sunrise Movement, all of which endorsed Sanders, and the Working Families Party and Progressive Change Campaign Committee, which endorsed Warren.

Unpledged groups include the Be a Hero Action Fund, Black Male Voter Project, Black Voters Matter Fund, Democracy for America, Inequality Media Civic Action, Justice Democrats, Presente Action, Progress America, and Social Security Works.

The call for unity follows a wave of infighting capitalized by Tuesday’s Democrat debate in Des Moines, Iowa.

CNN’s Abby Phillip asked Sanders about the report alleging he told Warren during a private meeting in 2018 that he did not believe a woman could secure the presidency. Sanders denied the allegation prior to the debate and during the debate. Nonetheless, Phillip asked Warren about the rumored conversation, presenting the allegation against Sanders as fact.

“Sen. Warren, what did you think when Sen. Sanders told you a woman could not win the election?” she asked.

“I disagreed,” Warren said, taking no issue with the way Phillip framed the question.

The Massachusetts senator refused to shake Sanders’ hand following the debate, signaling icy tensions between the two.

“I think you called me a liar on national TV,” she told Sanders.

“You know, let’s not do it right now. If you want to have that discussion, we’ll have that discussion,” Sanders said.

“You called me a liar. You told me — all right, let’s not do it now,” he added, walking away:

That exchange was emblematic of the rising tensions within the Democrat Party. CNN faced a flurry of criticism for “rigging” the debate against Sanders, and #NeverWarren, #WarrenIsASnake, and #CNNIsTrash trended after the two-hour event.

Sanders’ wife, Jane, is also calling for party unity, making her plea in a tweet posted Wednesday afternoon: