The same people on here who regarded him as the progressive messiah and Second Coming of Franklin D. Roosevelt in 2008 would throw him under the bus and call him an establishment sellout for supporting the evil neoliberal warmongering corporatist shedevil over the "true progressive fighting champion Freedom Fighter Bernie Sanders."
lol. One of the funnier things I noticed in an article about Elizabeth Warren was that the Bernie people are ready and willing to throw her under the bus and call her a sellout establishment corporatist if she endorses Hillary. Yes, the very same people that were donning "Ready for Warren!" stickers earlier in the year until they needed to settle for Sanders as their fallback option. Funny stuff.
Anyway, I think an endorsement before Iowa would raise her odds by a decent amount. Maybe from 60% to 80% or so? Before NH would help her, but probably not enough to change the outcome. Endorsing after NH would be the best scenario for her, since it would lock down SC/NV (assuming they weren't already locked down), which will lead to Sanders getting neutered on Super Tuesday.