On Wednesday morning, Sen. Bernie Sanders, I-Vt., is set to unveil a bill that would make Medicare universal with the co-sponsorship of at least 15 Senate Democrats. The legislation would finally make health care a human right for all Americans.

The question is: What do proponents think will make this push for single payer any more successful than others in the past? After all, activists who backed such an approach during 2009’s health care debate were literally arrested at hearings, and their legislation was sidelined and never even brought to a vote.

But this time, as he launches his campaign, Sanders has the support of 24 grassroots organizations with a combined membership base of tens of millions of people. Here they are:

Our Revolution: The grassroots group formed from Sanders’s presidential campaign list; it is led by former Ohio state Sen. Nina Turner. Social Security Works: President Nancy Altman and Executive Director Alex Lawson helm Social Security Works, which has for years worked to protect the Social Security system from cuts and expand its benefits. It has well over 1 million members. National Nurses United: The nation’s largest nurses union and has made single-payer health care one of its top legislative priority for years. Progressive Campaign Change Committee: A million-member progressive grassroots organization led by Adam Green and Stephanie Taylor. Democracy for America: DFA was formed from the network that coalesced around Howard Dean’s presidential campaign. Labor Campaign for Single Payer: The single-payer advocacy wing of many major American unions. LULAC: T he League of United Latin American Citizens is the nation’s largest and oldest Hispanic advocacy organization. Working Families Party: A progressive political group founded in New York that has since spread across the nation. It works to recruit, train, and elect progressive candidates, often in Democratic primaries, and occasionally on its own ballot line. MoveOn: A national progressive grassroots group with millions of members. AllOfUs: A youth-driven social activism group founded by activists who supported Sanders’s campaign. Demand Progress: A major social activism group that works on issues ranging from civil liberties to net neutrality. Health Care Now: A coalition of activist groups founded in 2004 to establish single-payer health care. Progressive Democrats of America: A political action committee dedicated to empowering progressive Democrats. CREDO: A fusion progressive organization and phone company that uses its revenues to fund activism. It has more than 5 million members. Public Citizen: This Ralph Nader-founded civic activism organization has been the driving force behind landmark consumer legislation for decades. Latinos for Healthcare Equality: A New York-based nonprofit that works to increase health care access. Americans for Democratic Action: ADA has spent 70 years supporting progressive causes. It was a major force during the push for the Great Society, but has languished since. AIDS Healthcare Foundation: This Los Angeles-based nonprofit, which provides treatment for HIV-positive patients, was one of the driving forces behind the 2016 drug-pricing initiative in California. DailyKos: A hub for liberal bloggers founded in 2002 opposed to the Bush administration, which has an active email list of millions of people. Food & Water Watch: This nonprofit works on government and corporate accountability related to our ecosystem. Friends of the Earth: A grassroots environmental group; its parent group has 2 million activists in 75 countries. 350.org: This group, founded by environmentalist Bill McKibben, fights to keep fossil fuels in the ground and for a clean energy future. International Association of Machinists and Aerospace Workers: This union represents nearly 600,000 workers. American Sustainable Business Council: The only business group on the list, the ASBC represents a number of American companies who believe that progressive policies, like single-payer health care, are good for the country and good for business.

In an email to his campaign list sent earlier this month, Sanders described the grassroots organizing that will go into passing universal Medicare as similar to a presidential campaign.

“There will be rallies, buttons, bumper stickers, shirts and most importantly people organizing in their communities across the country,” he said. “This is not going to be a quick or easy fight. We’ll be taking on the insurance companies, the drug companies, Wall Street and all those who make billions in profit from the current dysfunctional system.”