A fascinating article from political scientists Christopher Achen and Larry Bartels:

[C]ommentators who have been ready and willing to attribute Donald Trump’s success to anger, authoritarianism, or racism rather than policy issues have taken little note of the extent to which Mr. Sanders’s support is concentrated not among liberal ideologues but among disaffected white men.
More detailed evidence casts further doubt on the notion that support for Mr. Sanders reflects a shift to the left in the policy preferences of Democrats. . . .
[Sanders supporters] were less likely than Mrs. Clinton’s supporters to favor concrete policies that Mr. Sanders has offered as remedies for these ills, including a higher minimum wage, increasing government spending on health care and an expansion of government services financed by higher taxes. It is quite a stretch to view these people as the vanguard of a new, social-democratic-trending Democratic Party. . . .
[Y]oung Democrats were less likely than older Democrats to support increased government funding of health care, substantially less likely to favor a higher minimum wage and less likely to support expanding government services. Their distinctive liberalism is mostly a matter of adopting campaign labels, not policy preferences.