When Bernie Sanders announced he would run for president as a “democratic socialist,” few believed it would amount to much. Then, against all expectations, Sanders drew massive crowds, commanded high levels of favorability in almost every demographic category (including overwhelming support among young people), and raised hundreds of millions in campaign dollars from small donors.

Not least, he came within a few percentage points of beating Hillary Clinton, a frontrunner once assumed to be unassailable.

Waged by a candidate who had never run as a Democrat before and has declined to do so in the future, the Sanders campaign has revived hope that a serious electoral politics to the left of the Democratic Party might be possible.