but I think a strong Dem can rally the base while also highlighting issues that matter to the non-ideological voter without asking voters to accept a dramatic shift in their perception of America.
I understand this point. However, I would argue that those voters tend to support the policies progressives are putting forward. Plus, someone like Sanders comes across as genuine and not disingenuous as some of the establishment-style candidates do. This too helps with those types of voters IMO.
The notion that non-ideological voters or independents or whatever you want to call them aren't going to support a strong progressive is wrong in my opinion. I think enough of them (to form a broad coalition) would support a strong progressive even given the chance.