In a remarkably short time, Bernie Sanders and his revolutionary movement have become a stunning influence in American politics. Sanders supporters have won 22 state primaries, gained about 45% of convention delegates, contributed 228 million dollars to the campaign through 2.5 million donors, and gathered together in rallies in numbers approximating a million and a half enthusiasts. It is a force that can potentially reshape American political life—but will it hold together after the 2016 campaign comes to an end in July of 2016? That is a “berning” question for the Sanders camp and for politicians generally.

The Sanders phenomenon is different and unique; it’s a hybrid of an electoral party campaign and popular insurrection, intertwined. That makes it hard to figure out and slippery to prognosticate about.

The Sanders movement is composed of roughly 12 million supporters who voted for him in the Democratic primaries. This aggregate of adherents is in part an electorate and in part a movement. Mass movements rarely function within political parties and their leaders ordinarily keep their distance from established party structures. The Sanders phenomenon is different and unique; it’s a hybrid of an electoral party campaign and popular insurrection, intertwined. That makes it hard to figure out and slippery to prognosticate about.

We know something about the makeup of this maverick group from voting statistics. Predominantly, the group is young—a recent Tufts University study reporting that a larger number of young people under thirty voted for Bernie than for Hillary Clinton and Donald Trump combined. A second key feature is that it has a high proportion of independents, people who typically avoid a party affiliation. Bernie supporters also lean toward the white and male demographics. Otherwise, they are a diverse and polyglot group with critical differences across many dimensions. They vary in their specific political outlook and goals, previous electoral participation, and sophistication in politics. Their ranks include liberals, progressives, radicals and socialists.

In more descriptive language, they can also be depicted as:

Democratic Party regulars who supported Sanders in order to nudge Hillary to the left and reform the Party, with or without Hillary in the White House.

Democratic Party regulars (like the Progressive Democrats of America) who wanted to transform the Party, specifically by means of a Sanders presidency.

People with loose but continuing ties to the Democratic Party, some of whom have wanted the campaign to reform the Party marginally and some of whom wanted the campaign to transform the Party drastically in a progressive, populist direction.

Young people and students looking for new and more powerful policies to address their issues—crushing college debt, low salary jobs, climate change anxieties, etc.

Young people and students taken with Bernie’s ideals and wanting to change the world.

Young people and students who were following the latest trend among their peers, without much depth, as in the days of the student movement of the 60s.

Socialists and radicals of disparate shadings who have thought Bernie could advance some of their agenda (economic equality, free college) and provide scaffolding for promoting socialism.

Socialists and radicals of disparate shadings who viewed Bernie supporters as a pool of dissidents who were potential recruits for their organizations.

People who were attracted to Sanders because he ran a campaign to keep money out of politics, shunning super pacs and corporate funders.

People who were attracted to Sanders because they viewed him as an honest, ethical, and genuine figure in American politics.

It’s obvious that there isn’t substantial representation among supporters from African-American and minority ethnic groups and from organized labor, with important exceptions—African American influentials like Cornel West and Benjamin Jealous and unions like the Communication Workers of America and National Nurses United. Whatever Sanders does in the future, engaging these groups broadly has to be a high priority.

There are no doubt additional ways of slicing and describing the Bernie pool of supporters. The depiction above should be sufficient to show that this is not by any means a unified collectivity. Should Bernie lose the ultimate nomination in late July in Philadelphia, as is fairly destined, this diverse collectivity is all but certain to fragment substantially. We’re already seeing that split in the strife between Hillary stalwarts and the Bernie-or-Bust crowd.

Only continued forceful leadership by Bernie can hold his band of revolutionaries together. Followers have consolidated around Bernie’s message, his persona, and the common task of getting him elected—against the odds. Without the concentration on gaining an election victory, splinters are bound to develop—socialists vs. progressive Democrats, independents vs. party regulars, older moderate Democrats vs. radical millennials. The goal and the approach that Bernie chooses as the focus of his leadership will attract some of his cohorts and turn away others. The strategic options he has include keeping both feet in the Democratic Party, keeping one foot in and one foot out, or keeping both feet out. I’ll describe them and give my preference.

The Party establishment and media pundits are driving Bernie toward the “keeping both feet in the Party” option. Implant yourself firmly in the Party, push for a strong platform statement, nab a prime time speech at the convention, and advise your supporters to vote for Clinton and defeat Trump. In taking that tack, Sanders could get a high level administrative appointment and be well-placed to promote the policies he favors through the party apparatus. This would keep the Party regulars among his supporters with him and bring in some others also. But those on the left, and many others, would abandon him for kowtowing to Hillary Clinton, giving aid to a neoliberal candidate, and bolstering a status quo corporate party wedded to maintaining the dominance of the billionaire class.

The “one-foot-in-and-one-foot-out” approach embodies the stance Sanders has had as an Independent who serves as a member of the Democratic Caucus in the Senate. He could operate within the Party (trying to alter it drastically at the same time), but also support hundreds of down-ballot progressive candidates, both candidates affiliated with the Party and change-oriented newcomers. He would concurrently promote issue-oriented community groups to bring an end to police brutality, raise the minimum wage, stop gender inequality, aid the homeless, and push for climate justice. Sanders could set up a national independent action organization composed of his members and drawing on the campaign structure to promote those objectives. Howard Dean, after the 2004 campaign, established Democracy for America along similar lines—without much impact in his case. The dual approach of working in the Party and outside of it would probably attract the largest cross-section of Sanders’ campaign supporters.

The “both feet out” posture means that after the election Bernie would embrace the independent party posture that has dominated his long-time political career. He would opt for building a third party with a strong democratic socialist component, as has been urged by Jill Stein of the Green Party and Seattle City Councilperson, Kshama Sawant, of Socialist Alternative, and others. That involves carrying over the impressive campaign infrastructure he has produced to build a true and unambiguous left presence on the American political scene. This approach would attract left and radical components among his adherents, young people, and also restless and disenchanted elements across the rest of his supporter spectrum. Party loyalists and moderates would certainly pull away.

The Sanders campaign has legitimized socialism and political revolution as part of the dialogue of US politics and established the most fertile grounding, possibly ever in American politics, for creating a viable third party. The campaign has generated supporters in the multi-millions, a striking army of volunteers, dedicated staff, an astonishing number of small donors, highly sophisticated campaign technology, and that famous momentum. In all probability, Sanders will select the second option I described involving an inside/outside strategy. That would likely have the highest comfort level for him, given that in recent years he has combined running as an independent with active participation in the Democratic Caucus.

The third option, constructing a new independent party, would be more contentious, intense, and difficult to carry forward. But arguably, it would have the strongest impact on revitalizing and humanizing American politics. The Democratic Party, considering its intermeshed dalliance with Wall Street, is a dubious vehicle for taking the Sanders program much beyond a lofty-sounding platform statement.

Sanders, an avowed democratic socialist, frequently laments that the US is the only Western democracy deficient a universal health system. But it is also the only one that is absent an organized left in its political life—limiting the range of policies the nation can mount and the choices citizens have about how to address their problems. As an ardent advocate for correcting the first deficiency, it would be entirely fitting for Sanders to seek also to remedy the other one.

Jack Rothman