I am a big fan of the political economist Mark Blythe.  He recently gave a talk at my alma mater the University of Nebraska-Lincoln on, basically, how we got into this mess.  The mess being Trump, Brexit, and the rise of populism around the world.  You can watch the video here.  The whole talk is worth while but at the end (45:24 mark) he lays out five policies which he speculates might stem the populist tide.  The policies are generally in line with what left-wing populists have been arguing for so they will in general placate them and conversely undermine support for right wing populists.  The five policies are:

1. Free College
2. Subsidized Childcare
3. Single Payer HealthCare
4. Corporate Reform of “Shareholder Value” Culture
5. Break Up Digital Monopolies

Along with a policy of “Everyone Pays Their Taxes” I think these 5 could make a very effective platform for the Democratic Party in 2018 and 2020.