That’s what Peter Beinart argues in this Atlantic piece:
By conventional standards, Sanders’s candidacy is absurd: He’s not well known, he doesn’t have big money donors, he’s not charismatic, and by Beltway standards, he’s ideologically extreme. But candidates with these liabilities have caught fire before. Think of Jerry Brown, who despite little funding and an oddball reputation outlasted a series of more conventional candidates to emerge as Bill Clinton’s most serious challenger in 1992. Or Pat Buchanan, who struck terror in the GOP establishment by winning the New Hampshire primary in 1996. Or Howard Dean, who began 2003 in obscurity and ended it as the Democratic frontrunner (before collapsing in the run-up to the Iowa Caucuses). Or Ron Paul, who in 2012 finished second in New Hampshire and came within three points of winning Iowa.
What did all these insurgents share? They gave authentic voice to the grievances of their time.
The real value in a Sanders campaign is what is does to Hillary Clinton’s. Does he force her to the left and outside the national election mainstream? Or by comparison does he make her appear to be the moderate middle?