Last week, just after winning the Indiana primary, Bernie Sanders vowed to stay in the Democratic presidential race until the last primary, on June 14. “I think we are perpetuating the political revolution by significantly increasing the level of political activity that we’re seeing in this country,” he said regarding why he won’t drop out of a race that is increasingly unlikely for him to win. This “revolution” grew out of public recognition that the grievances and aspirations of average Americans were being ignored by the most politicians, and Sanders’s ability to attract nearly half of Democratic voters shows that a broad base exists for an independent challenge to the party establishment. Over the past decade, we’ve also seen large protests erupt in the United States through Occupy Wall Street, Black Lives Matter, and movements for immigrant rights and climate justice. But how can this energy translate into electoral power in our rigid two-party system? Progressives might take a page from the inside-outside strategy embraced by the Tea Party.

Inside and Outside

While over a thousand third parties have been formed in the United States, only a handful have ever won over more than 5 percent of the vote—and most die out after a couple of election cycles. That’s because in our first-past-the-post system third parties have virtually no chance of winning a majority of voters on a national scale. In proportional systems, if you win 15 percent of the vote, you get 15 percent of the seats. In our system, if you win 15 percent of the vote, you typically receive no seats at all. In proportional systems, new parties often translate protest in the streets into political institutions. In our system, with its high barriers to entry for new parties, protest movements who want to reach for electoral power can only manifest themselves through the formation of emergent factions within existing political parties.

The Tea Party movement, which emerged in 2009 following Barack Obama’s inauguration, has all but transformed—if not taken over—the GOP. It functions much like an independent third party: an ideologically uncompromising alternative for conservatives frustrated by the big-business and immigration-reform wing of the GOP. But instead of creating a third party to challenge Republicans in general elections and risk conservative defeat, they challenge incumbents in primaries—redefining the mainstream of the party in the process. Tea Party primary challenges have moved the GOP rightward toward a more aggressive agenda of cutting government spending and blocking immigration reform at whatever cost—including a government shutdown. As one right-wing blogger put it: “The Tea Party’s impact in primaries is largely about putting fear into establishment candidates, whether they knock them off or not.”

For progressives, the biggest lesson to be learned from the Tea Party’s playbook is that they don’t work for the Republicans—they make the Republicans work for them. Bernie has already begun to do the same with the Democrats, and his primary race should encourage others to challenge establishment Democrats from the left. The progressive formation that has perhaps made the most headway in this regard is the one I work for: the Working Families Party. The WFP is a coalition of community-organizing groups and labor unions that push progressive policies, like paid sick leave, and help elect a new generation of leaders on the state and local level. While we’re proud of what we’ve built, we’re a long way from the ideological and electoral power that the Tea Party exercises. The WFP has figured out how to maneuver inside and outside the two-party system without falling prey to the usual failures of third parties, and is now organizing in 11 states. But the Tea Party has taken over Congress, and done so without an institutionalized party apparatus. Neither the WFP nor a prior, important effort to launch a Tea Party of the left—Rebuild the Dream—have generated the kind of momentum and mass participation of the Tea Party.

Giving Away the Keys

An overlooked aspect of the Tea Party’s success has been its decentralized and open-source brand. The party doesn’t belong to any one politician or organization; it belongs to the conservative movement. Such an approach has enabled the Tea Party to gain so much popularity that 17 percent of Americans identify as party members, even though there is no institutionalized “party” or ballot line to speak of.

Part of the Tea Party’s success has been its ability to rally a conservative base and have institutions follow its lead. By generating headlines through large anti-tax marches, heralding defeats of members of the Republican establishment, and engineering polarizing events like government shutdowns, the Tea Party is constantly oriented toward asymmetric political drama capable of activating its own base.

Decentralized movements like Occupy and Black Lives Matter have similarly enabled mass participation among millennials by giving away ownership of the movement brand for anyone to run with. But more established progressive institutions have been reluctant to turn over the keys to party-building and electoral organizing to a mass base.

While no existing progressive organization has the capacity to adequately absorb and engage the base that has coalesced around Sanders, his supporters could get behind the new formations that will inevitably emerge. None of the existing organizations could sustainably fund the number of organizers to manage and direct a volunteer base of this magnitude–but more importantly, many of the millennials that are driving the Sanders campaign wouldn’t join a traditional organizational structure; it’s not what they are looking for. They are looking for channels that allow them to unleash their creativity and passion through self-organization and co-creation.

The Party Is “a Field of Struggle”

An overlooked aspect of our two-party system is the largely administrative nature of political parties in the United States. In a parliamentary system, parties develop candidate-lists up and down the ballot, from school board to parliament. But in our system, anyone can theoretically gather the required number of signatures on an official party form and be placed on a ballot in a primary election. The party then plays a purely administrative role, rather than a programmatic or disciplinary one.

When independent candidates like Bernie Sanders or Donald Trump compete in primaries, their decisions have less to do with their feelings about either party and more to do with what the party’s mechanisms allow access to. It’s the same as when citizens register to vote and select a party designation in order to participate in the primary season. Registering as a Democrat does not make people into party members in any way. It’s simply another way that the party holds a bureaucratic function to organize electoral activity.

A new party could therefore have its own accountability mechanisms, membership models, and decision making structures, but would immensely benefit from using the existing tools of the major party’s administrative machinery: primaries, ballot access, petitions, conventions, and the party-line vote used by an increasing number of voters.

Over time political parties in the United States have grown more permeable to outside forces. Progressive forces have informally or formally anchored themselves within the Democratic Party over the past near-century. Compared to parliamentary parties, the Democratic Party does not unilaterally shape a political agenda, but it is relatively responsive to the perceived desires of a coalition representing a majority of an electorate. Unite and activate public opinion in favor of a different direction, and the party tends to move, as Hillary Clinton’s slow drift leftward has already demonstrated. As Bill Fletcher put it in 2005, “Activists should look upon the Democratic Party as itself a field of struggle.”

Forward Together

A “party” made up of a New American Majority also requires new leadership. It requires white male progressive leaders willing to step back in order to make space for people of color and women to lead. But it also requires leaders of color to step up and help lead a coalition that includes many white people in order to form a winning electoral majority.

The rise of the Sanders campaign has also shown the appeal of a populist platform with working-class white voters who do not typically refer to themselves as progressives—or even Democrats. A multiracial coalition that speaks directly to the relationship between racism and oligarchy could provoke a transformative political realignment. Such an approach could put together an independent coalition that the Democratic Party could not take for granted.

Such a party would limit itself if it resonated only with a small set of constituencies. It requires not a laundry list of grievances and identities but a new collective identity and compelling narrative—an “us”—that is much greater than the sum of its parts. It means conveying a new sense of “the people” not solely on the basis of shared suffering but through a shared will to craft their own democratic destiny. It must give its base a real sense that they are the creators of the path toward a democracy that works toward freedom and justice for all Americans against those in our country who have in every era stood by the belief that freedom and justice were only meant for a select few.