Bernie Sanders, who for decades has described himself as a democratic socialist, is now the front-runner for the Democratic Presidential nomination—a position he could solidify by winning a majority of the fifteen primary contests being held on Super Tuesday. Sanders is running on a more ambitious platform than most American voters have seen in their lifetimes, promising to create a single-payer, national health-insurance program; to offer free tuition at public colleges and trade schools and to cancel student debt; and to launch a Green New Deal, which would fully transition electricity and transportation to renewable energy within ten years.

Many Democrats have objected to the sweeping ambition of Sanders’s proposals, questioning whether they can actually be passed and implemented and voicing concerns about whether Sanders’s vision of an expansive welfare state is in keeping with the Democratic Party’s agenda. To talk about the Vermont senator’s campaign and its place in the annals of American progressivism, I recently spoke by phone with Michael Kazin, a professor of history at Georgetown University and a co-editor of Dissent; he is currently writing a history of the Democratic Party. During our conversation, which has been edited for length and clarity, we discussed the ideological similarities and differences between Sanders and Franklin Delano Roosevelt, the distinctions between socialism and left-wing populism, and whether Sanders’s rise in a time of political upheaval is less shocking than people think.

Bernie Sanders likes to say that his proposals aren’t very radical if you take a long view of American history. Do you agree with that?

I agree and disagree. On the one hand, he’s channelling F.D.R. rather than Eugene Debs. He’s saying he’s going to complete the New Deal, and he talks about the Four Freedoms, which F.D.R. talked about in his State of the Union Address in 1941. So, in a sense, he’s going along with the social democratic tinge of the New Deal and arguing Roosevelt would be supporting Medicare for All, free college, the Green New Deal, that F.D.R. would be wanting to strengthen labor unions and tax the rich, and that he—Sanders—is not out of the mainstream of the progressive wing of the Democratic Party.

On the other hand, he calls himself a socialist, which F.D.R. never did, because he wasn’t. The fact is also that Sanders is running in some ways against the so-called Democratic establishment and has never really become a Democrat, and he wants to transform the economy as utterly as he can. That would make him the most left-wing candidate for President that any major party has ever nominated. He’s sort of straddling a more legitimized politics—with more mainstream rhetoric within the mainstream Democratic Party—with ambitions which will clearly go beyond what any Democratic nominee has ever stood for. He seems very shrewd about that, because on the one hand, clearly, a lot of his policies are popular. On the other hand, as we know from polls, most Americans don’t like the idea of socialism.

Why did F.D.R. decline to call himself a socialist? Was that for largely political reasons, or was there something about his policies that separate them from Sanders’s policies, or the policies of other socialists?

First of all, there was a Socialist Party in the nineteen-thirties, led by Norman Thomas, a Presbyterian minister. And they thought that F.D.R.’s policies were far too timid, because they really wanted to bring about a socialist society, not just a reformed capitalist one. And F.D.R. was very much in the tradition of the Democrats, from William Jennings Bryan to Woodrow Wilson to Al Smith in the nineteen-twenties, who wanted to give working people more power in the society. But they were really trying to make sure that capitalism would be able to serve the needs of most people. They wanted what you might call a moral capitalism, which they thought would be able to promote growth and more equity in the society but at the same time stay away from any kind of state ownership. The public-works jobs created in the New Deal, for example, through the Works Progress Administration (W.P.A.), the Civilian Conservative Corps (C.C.C.), and some of the other alphabet agencies were never intended to be permanent. The government was only supposed to be an employer of last resort during the Depression. Socialists at the time wanted to go much further than that.

After World War Two, most socialist parties in Europe gave up the idea of the total transformation of society and became what we now call social democrats, putting into place robust welfare programs, public housing, free or cheap transportation, and later on environmental regulations. They gave up the dream of a worker-controlled society, and I think Bernie Sanders has done that, too. But by calling himself a socialist, I think he leaves the way open for some of his supporters who really do want to go to a purely democratic-socialist society.

And also, Bernie’s background is pretty different from Roosevelt’s. Roosevelt was a rich guy, had some rich family, and didn’t want to do away with all rich people, whereas Bernie pretty much does. I mean, peacefully do away with them.

Populism is another subject you’ve written a lot about. How well do you think the label “populist” applies to Sanders?

I think Sanders uses populist rhetoric of a certain kind, as Trump uses populist rhetoric of a certain kind. Populist rhetoric is available to many different so-called outsiders in American politics. Bernie’s populism, of course, is left-wing populism, which speaks to or for a large majority—the “ninety-nine per cent,” undifferentiated by race or ethnicity or national origin or religion—against the economic élite. A more right-wing populism, like Trump’s, speaks to the white middle of the population against certain élites at the top, especially cultural élites and the media and former liberal governing élites. It is also very suspicious of the alleged unspoken alliance between the liberal élites at the top and people of color, especially immigrants, at the bottom. And that’s a traditional kind of populism going back to the Ku Klux Klan in the nineteen-twenties, which had a very similar kind of rhetoric as Trump, although, of course, a lot of the references are different.

How much do the history of American left-wing populism and the history of American socialism intersect or overlap? How would you differentiate between those two things?

Socialism is a much more explicit, well-defined doctrine, which includes specific, well-defined policies: the ownership of major means of production, a larger welfare state, more powerful unions, civil liberties for all, especially those who dissent from conventional economic doctrines. Whereas my definition of populism—and some people disagree with it—is as a way of talking about politics or a way of talking about “the people” as a moral group, a hardworking group beset by immoral élites. And the definition of the élite changes depending on who’s talking about it, and the definition of the people changes depending on who’s talking about it as well.

So socialism is a doctrine, it’s an ideology, it has a history—an organizational history, a movement history—whereas, from my point of view, though populism began with a movement and a party in the eighteen-nineties in this country, it sort of slipped the boundaries of that particular historical reference. And it’s now all over the place. You can find people talking about populists on the right, on the left, in the center. It’s really a way of opposing the people to the élites, and what matters are the definitions of the élites and the people. There are no populist policies in the way there are socialist policies.