Paul Simon ran on a Federal jobs guarantee program in 1988
(I mean the bow-tied Senator, obvs, not the singer-songwriter)
He lost to Dukakis but he wasn't particularly the "far left" voice in the primaries (that was Jackson), he was more dismissed as a wonky technocrat than as "too extreme" (my initial primary picks from 1988 on have been Simon, Tsongas, Bradley, Clark, Richardson, and O'Malley, so apparently "wonky technocrat" really does it for me).
Personally I've soured on the idea in a lot of ways (where are these jobs going to be? Are we really paying to keep West Garbut, Iowa, in existence, and why? Do we actually have work we need done, and if not wouldn't it be better to just give people a basic income? etc.) but I think it's important that it wasn't a particularly "extreme" idea 30 years ago. (This works both ways, of course: no Presidential candidate in 1988 would touch gay marriage with a 10 foot pole, whereas it's not particularly conceivable that a serious D candidate could be against marriage equality today -- also there were anti reproductive choice Democratic candidates back then, which isn't something you'll see at a national level now and even at a local level it's becoming rare. Also Simon was what we would today call a "hawk", one of the main voices urging for the intervention in Haiti and repeatedly tried to get us to intervene in Rwanda. Also he invented the "v-chip" to keep violent tv shows away from kids. Changing political coalitions are weird sometimes.)