Nearly 400 Democratic delegates plan to oppose any party platform that does not include “Medicare for All,” saying the coronavirus pandemic illustrates the urgency.

“This pandemic has shown us that our private health insurance system does not work for the American people. Millions of people have lost their jobs and their health care at the same time,” Judith Whitmer, a delegate for Sen. Bernie Sanders (I-Vt.) who chairs the convention’s Nevada delegation, told Politico. “There’s people leaving the hospital now with millions of dollars in medical bills. What are we going to do about that?”

The pledge, signed by more than 60 delegates, predominantly Sanders supporters, notes that “millions of Americans have lost their healthcare insurance because of those job losses at a time when healthcare is needed most” and that “the Democratic Party and their Platform Committee process has failed, to date, to incorporate a clear and progressive platform plank for Medicare-For-All for adoption by the 2020 National Convention.”

Presumptive Democratic presidential nominee Joe Biden has made his opposition to Medicare for All clear, and the pledge comes as Sanders supporters have largely united behind Biden. Sanders endorsed Biden shortly after his withdrawal from the race. Two leftist advocacy groups, Progressive Democrats of America and RootsAction.org, announce their support of the petition Monday, with organizers expecting the petition to garner hundreds more signatures.

“The sea change that’s underway could swell as a result of this initiative,” RootsAction.org national director Norman Solomon, a Sanders delegate, told the publication. “It’s a reasonable hope that historians will look back at the next couple of weeks as a time when hundreds of delegates stepped forward and said, ‘This is a red line for a humane society and we’re not going to stop saying so.’”

The leaders behind the pledge said they remain committed to voting for and supporting Biden, with RootsAction.org still committed to spending hundreds of thousands of dollars on boosting the former vice president in swing states, according to Politico.

“We’re going to fight like hell for Biden. And there’s no contradiction between doing that and supporting this pledge,” Solomon told the publication.