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.