A pair of national progressive organizations that endorsed Sen. Bernie Sanders in the 2020 Democratic presidential primary has published an open letter urging presumptive nominee Joe Biden to select Sen. Elizabeth Warren as his running mate in order to “unify the party and take back the White House.”

“Few senators have fought harder and more consistently for the kinds of structural reforms that would lift up working-class families and communities,” the groups wrote. “Senator Warren has also proposed some of the most comprehensive policy plans to deal with the consequences of the coronavirus pandemic. She has the tenacity and expertise to help ordinary Americans steer through this crisis, and she’d be ready to govern on day one.”

Biden—who has vowed to pick a woman as his running mate—is reportedly considering more than a dozen candidates for his vice presidential pick, including Warren, Sen. Kamala Harris (D-Calif.), Rep. Val Demings (D-Fla.), and Michigan Gov. Gretchen Whitmer.

With Biden facing calls from a number of Democrats and pundits to select a woman of color as his running mate, some Black progressives have urged the former vice president to pick Warren—and recent survey data suggests that the Massachusetts senator is the most popular choice among Black and progressive voters.

“Folks are saying we need a Black woman, and I understand where they’re coming from,” Angela Peoples, the director of the organizing group Black Womxn For, told The Hill last week. “But what’s most important and what needs to be prioritized is leadership that is committed and is pushing for these big structural shifts in our country and people who are rooted and listening to our community.”