Now that Sanders has dropped out--a commendably responsible move in my view--the post mortems have begun in earnest. We now have two successive failed campaigns for fhe nomination to look back on and it seems highly unlikely he will run again.
So what did he accomplish?
The consensus of the left--and I think it's fair--is that he helped move the entire political conversation in America to the left and create space for much bigger policy ideas than had been the case before 2016. In other words, the famous Overton Window has been moved to the left and that's a good thing. Of course, the country didn't move left just because of him but he did play an important role in channeling existing outrage at inequality and the multiple deficiencies of contemporary American capitalism into a concrete and progressive political form.
But there is another side to Sanders and I think his left supporters would be wise to think about it long and hard. Simply put, he didn't really know how to win. Putting together a majoritarian coalition in American politics is hard, both within the Democratic party and the general electorate. Sanders simply did not have a good idea of how to do this, relying instead on untenable assumptions about the appeal of his uncompromising brand of politics. In particular, as Perry Bacon Jr. argues:
"Sanders and his aides..made new mistakes in 2020. There were some clear indications that some of Sanders’s success in 2016 — among white voters without college degrees, in particular — had more to do with anti-Clinton sentiment than strong support for Sanders. But the senator’s advisers seemed to think that Sanders had a unique appeal to white working-class voters that would simply continue in 2020. So the Sanders campaign decided to invest heavily in the March 10 primary in Michigan, a state packed with white voters without a college degree. Biden not only won Michigan easily, but he won overall among white voters without a college degree (and pretty comfortably).
Sanders stayed in the race for about a month after Michigan, but that loss was really the end of his campaign. It undermined one of Sanders’s central arguments — that his brand of politics appealed to white voters without a degree in a way that the more centrist vision of Biden and Clinton did not, making the Vermont senator a stronger candidate than Biden in the general election.
Sanders and his team also expected that he would boost turnout among younger voters. This did not pan out."
Moving the Overton Window is a great thing. But it is only a necessary, not sufficient, condition for progressive advance. You still gotta win and for that you need a broad coalition. One hopes that his supporters internalize that lesson.