You could argue that the “Abundance” Democrats fall into this group, as they have been mostly sidelined. Al Franken and Howard Dean come to mind as well. Dean’s exit was particularly painful as his (somewhat obvious) 50 state strategy succeeded in 2007 and 2013, and resulted in a party that was more flexible and responsive to material regional concerns. As an independent voter, this was a huge improvement over any party organization before or since.

I think it depends on how you characterize “reformist”. I’m almost certainly being too loose with this term. I mean people who actually push hard for substantial reform, including deep technical reforms, not the common colloquial meaning of incremental, superficial reform from groups like the New Democrat Coalition. Frankly I probably should have used a different word, as I think my usage here is atypical.

What I mean is the somewhat awkward “non-mainstream liberals who advocate for substantial policy changes.” Maybe I should just say progressives? But the people I’m thinking of don’t quite fit in with most of the progressives, even if they do sometimes align with them. We don’t have Lib Dems like the UK does, but that would probably be the segment I’m talking about if we had that here.