Democrats used to be the conservative party before Nixon (my timing might be off) said "Hold my beer" and turned the Republicans into the regressive Christian theocracy it is today.
So, the civil war thing doesn't really count because it was a different party with different ideals under the same name.
He might be as close to a communist we have ever had with the New Deal, granting the right to unionize, Social Security, and all kinds of labor protections.