There is an outstanding article by Franklin Foer in this month's Atlantic Monthly: What’s Wrong With the Democrats? It is a long article, but quite good and I think spot on. It discusses what Democrats need to do to regain the votes of the white working class, a group that used to be a reliable base for them.
Of particular interest is his discussion, late in the article, of Senator Elizabeth Warren's views. Though she shows no interest in public, nor apparently even in private, of running for president in 2020, I think she does have a message the Democrats could profitably use. Warren, who indeed used to be a Republican and is a free market supporter, is according to this author not nearly as radical as the press makes her out to be, and in fact is very concerned with the concentration of power in ever fewer corporations, and the abuse of that power in politics by rent-seeking CEOs and the government officials they have purchased. That I think could very well be a message Democrats could build on successfully, if they could only drop their outdated identity-politics ideology.