Bernie Sanders’s endorsement of Hillary Clinton marked the end of the single most successful socialist presidential campaign in American history. Sanders got 13.1 million votes, or 4 percent of the US population. Even Eugene V. Debs in 1912, the previous high-water mark for socialist presidential bids, only received 900,000 votes, or 0.9 percent of the US population.

All of which raises the question: Where do American socialists go from here? How can they maintain the momentum of the Sanders campaign — and the grassroots organizing that Sanders has done — in service of socialist campaigns and causes in the future?

I asked Bhaskar Sunkara — the founder, editor, and publisher of Jacobin, a radical socialist magazine that's become a leading outlet of the American left — what the future of socialism looks like now that Sanders has conceded. We Gchatted on Thursday. A transcript, lightly edited for length and clarity, follows.

Dylan Matthews: What did you make of Bernie’s endorsement speech, and the whole runup to it, with Clinton reaffirming her support for the public option, coming around on free college, making concessions on the platform, etc.?

Bhaskar Sunkara: I think the past couple weeks has shown a lot of the promise and limits of Bernie Sanders' approach.

The battles over the platform were basically futile, if you're thinking from the standpoint of actual policy. But it wasn't terrible for movement building. Sure, I'd love other Bernie supporters to be thinking more about the things they can do outside the Democratic Party, but realistically that would have been too big a leap to expect.

Instead what you got was some contentious battles and something that people will hold Hillary Clinton to. And if she's unable to deliver, it'll only keep alive this wedge in the Democratic Party: between Sanders supporters — many of whom seem to be identifying to the left of liberalism — and the Clinton mainstream.

Clinton has to apologize for things like [the Trans-Pacific Partnership] now, the Democrat rank-and-file has shifted on Palestine in a good direction, the battle for Medicare For All was lost but it's still alive as a demand.

As for Bernie's endorsement, it's exactly what he said he would do. He said that he would support the Democratic nominee. His critics to his right were overheated saying he should have done it long before, and the "Bernie or Busters" mad at him aren't being fair. I would have rather he held a bit firmer until the convention though.

DM: What does keeping this wedge in the party look like, operationally? How does the Sanders wing keep itself going and keep applying pressure to Clinton?

BS: Right now, I think we have to be honest about how undefined the "Sanders Democrat" is. It's not like the Tea Party, which had strong existing networks to draw from — outside funding, think tanks and foundations, church networks.

Without more rigorous and ideological grounding, we’re likely to see the Sanders brand attached to a motley bunch of party dissidents. What connects someone like Rep. Tulsi Gabbard — who's had her fair share of nice things to say about [India’s strongly anti-Muslim Prime Minister] Narendra Modi — and [DNC Chair Debbie Wasserman Schultz’s primary challenger] Tim Canova with left-liberals?

Supporting them might make sense as a marriage of convenience, but one can't make those tactical choices without real restructures and shared principles. We'll see where efforts like Brand New Congress go, but they lack any organic base in communities and workplaces, so it's hard to see them holding anyone accountable.

That said, there's an opening to create those things and Sanders has shown a willingness to help push in this direction. The Left in the Sanders movement will have a hard time doing it without proactive help from what remains of the campaign.

DM: There's always been a minority of socialists throughout the primary arguing that Sanders was fundamentally closer to mainstream liberals like Clinton than he was to authentic democratic socialism. Him settling for a public option and means-tested free college seems to confirm that critique.

After all this, do you still think he was a good vessel for the left to align with?

BS: I don't want to sound glib, but it's America and it's 2016. You have a candidate who calls himself a democratic socialist, who talks a bit about socialist history, who has connected the rhetoric of "political revolution" to the struggle against inequality, who has the support of millions of people, and you're going to be upset that his program is just a social democratic one?

You can't just look at what the policies are, you have to look at where the impetus for the policies was coming from. The fact that there is perhaps a majority of the country favorable Sanders' social democratic ideas tells me that we have the change to build a more radical socialist opposition in our lifetime. Now, if the argument was that his campaign had to be engaged with differently and more critically because it was within the Democratic Party primary process, that's a fairer argument and one that Sanders himself would have probably agreed with most of his political career.

DM: On the "it's America" point, there is a degree to which these intra-left debates sometimes act as though disagreements over tactics say something about ideological positions.

So if, say, you're a democratic socialist who tactically thinks it's better to vote for Clinton than for Jill Stein in the general given the current situation, that codes as being more ideologically right-wing, when maybe the same person in a parliamentary system with party-list representation would be calling for votes for the Left Party because the Green Party’s too right-wing.

How do you think about those sets of questions? How different do the peculiar institutions of the US make optimal left strategy than what it'd be in other countries?

BS: I think maybe they come across that way: like that people are dealing with these questions abstractly and at the level of ideology. But the experience of history — since 1896! — tells us something about left movements in the Democratic Party. That isn't a moral argument, it's a strategic one.

I think the Left in the United States shares a mission with the Left in a lot of places. We need to fight for a party built around the distinct interests of workers. In Australia, they managed to build a workers' party out of what was originally a first-past-the-post system. In the United Kingdom they built the Labour Party. We know that it's possible. The question is how we get from here to there.

We don't have a good option on the ballot in November, and we can't swing a national election. But we do know that we have to foster tendencies in the labor movement and elsewhere that thinks of independent political action by workers as a goal and intentionally moves in that direction.

DM: What do you make of labor's record during the primary? A lot of major unions backed Clinton almost reflexively. Why was that? What would need to change to make unions a voice for the Sanders wing of the party?

BS: Labor's actions were pretty expected — Clinton is going to be the next president and there's little use from their standpoint in picking fights over losing battles with her.

A lot of people think that pushing those unions to the left ideologically is the way to make that kind of mentality change. But you can have left-wing leaders and still have the same practices in place. I mean, John Sweeney [the AFL-CIO leader from 1995 to 2009] was a socialist.

What we need to happen is rank-and-file democracy and insurgencies within the movement, things like what happened in Chicago with the rise of the CORE caucus within the Chicago Teachers Union. Once you have members actively involved in their unions, with a democratic say over their directions, then the politics will better reflect their interests and I think would be more militant.

One battle that happened throughout the past year was union members saying: "Me and all my friends support Bernie, who made the decision to endorse Clinton?" Bernie was used to open up questions about union democracy and accountability.

DM: What do you make of the "Bernie Congress" movement, his effort to back left-leaning candidates like Zephyr Teachout, Lucy Flores, etc.? How valuable is it to push Democratic nominees in that direction? Is it a viable long-term strategy for shifting the party?

BS: I think these could be worthwhile efforts, but a lot depends — like I said before — on what criteria is used for selection. Right now it's really unclear.

But my emphasis is elsewhere: I want to direct Sanders supporters outside of just electoral efforts — broadly to the networks of the left, to social movements, etc. It won't be all of them, it'll be minority, but hopefully they'll have a big enough platform (with the help of Sanders himself) to maintain enough visibility to connect to the broader group of voters who were inspired by him but aren't going to be in the streets any time soon.

What's key is that we build an identity and organizations to the left of liberalism. When I was at the People's Summit the other week, National Nurses Union president RoseAnn DeMoro said, "Liberals are usually bad, they usually sell you out when you think they’re with you." Everyone clapped. The rank-and-file nurses and others in attendance didn't consider themselves liberals.

That shows real promise for our effort to build something on the far-left that's relevant and actually has a social base. I don't think a more liberal-left Congress hurts us in that effort, though.

DM: I wanted to ask you about a specific example of that non-campaign organizing: Fight for 15, which just got into the Democratic platform and has won statewide in California. If there's a Democratic House, there's a very real chance that's national policy in the near future.

What can the left learn from that experience? What should a 21-year-old Sanders activist who wants to work on the next Fight for 15 do?

BS: I think it's proof that if you organize — and you organize workers at the point of production especially — you can impact policy in even the short term.

Being a radical isn't about being too pure for the world, it means getting involved in the nitty gritty effort to build politics. That's different than building policy. We're changing the conditions in which policy is written, not trying to be insiders.

Even a far from perfect campaign like FF15 was far more impactful than insider lobbying for labor. I think these are all valuable lessons [as] we try to build a visible left-wing opposition movement in this country.

DM: It seems like some of the energy backing Sanders in the primary is being transferred to efforts to back Warren for vice president. How do you place Warren — someone who identifies as liberal but also is very into naming the enemy and fighting corporate power — in the context of the effort to build a left-of-liberal movement?

BS: Warren is a mixed bag, but someone who I think does have a moral and ethical core to her politics that I respect. She's moved leftward over the course of her life. For now, she's a liberal ally on certain issues — not someone like Sanders who we should expect to help convene and organize these efforts.