Bovada has Biden at +200 and Warren at +700. Combine the implied odds (no vig adjustment, though), you get 46%. I don't think the market is perfectly efficient, but 50/50 is probably a pretty good estimate. At this point in the race, I'd probably rather take wai's side. It's funny, though, because Wai isn't betting based on a sophisticated understanding of the issue; he's just making the same mistake (underestimating the chances of candidates who aren't currently doing that well in polling) about a different couple of candidates.