The national grassroots group Indivisible set out Thursday to make sure the 2020 Democratic primary doesn’t devolve into a race characterized by negative attack ads, releasing a pledge for all the Democratic presidential candidates to sign which promises a “constructive” primary.

The pledge calls on the 21 presidential candidates to treat the primary as an exchange of ideas while respecting their opponents and to immediately support the eventual nominee, working together to “do the work to beat Trump.”

“We must defeat Donald Trump,” reads the We Are Indivisible Pledge. “The first step is a primary contest that produces a strong Democratic nominee. The second step is winning the general election. We will not accept anything less.”

 Indivisible, which was established after the 2016 election by former Capitol Hill staffers with the aim of guiding Americans in their resistance against President Donald Trump’s agenda, wrote in an email to supporters that it is thus far staying neutral in the primary.

“We don’t yet know when in the process we’d consider jumping in to support a specific candidate, or whether we’ll endorse during the primary at all,” wrote the group. “But we know that, above all else, we want to ensure that our entire movement is united in supporting the eventual nominee—no matter what,” the group added.

The pledge comes months into a campaign which has already seen the centrist Democratic think tank Center for American Progress (CAP) release a video on its news website, ThinkProgress, attacking Sen. Bernie Sanders for his wealth.

Sanders responded with a letter expressing “disappointment with the destructive role” CAP was playing “in the critical mission to defeat Donald Trump.”

“I and other candidates are running campaigns based on principles and ideas and not engaging in mud-slinging and personal attacks on one another,” Sanders added.

Sanders became the first candidate to sign the pledge on Thursday.

“Democrats do not need to choose between creating space for a healthy primary debate and taking back the White House in 2020,” said Maria Urbina, Indivisible’s political director. “Indivisible’s pledge invites candidates and grassroots leaders to join together in rejecting that false choice.”

Click Here: Rugby league Jerseys

In addition to asking the candidates to sign the pledge, Indivisible is inviting voters to promise that they will also help to ensure a positive primary campaign. A number of supporters, including local Indivisible chapters, shared on social media that they had signed onto the pledge.

“We believe in rigorous and spirited primaries, and we also know that once we have a nominee, our entire focus must turn to defeating Trump,” said Ezra Levin and Leah Greenberg, co-executive directors of Indivisible.

“This pledge is about beating Donald Trump and the anti-democratic, xenophobic right wing,” they added. “And it’s about the ideas and vision we need for a post-Trump future.”