Down-ticket candidates: he'll endorse progressive Democrats and help independents, if they are lucky.
Leave out the southern states, which Bernie and Hillary will lose anyway in the general election. Bernie can beat Hillary in the other states, where there were open primaries and would have beaten her in the ones that were closed.
Running for Senator in a rural state, Bernie pulled 70% of independents and 25% of Republicans, So, let's play with some numbers:
I predict:
Bernie Will get:
70% of the 40% of voters who are independent= 28%
35% of the 30% of voters who are Democrat = 10.5%
15% of the 30% of voters who are Republicans= 4.5%
so Bernie will get 43% total
That leaves Hillary and Donald to fight over 57% of the balance of voters.
Trump will probably get
70% of the remaining 12% who are independents 8.4%
90% of remaining 25.5% who are Republicans (some will stay home, some will vote for Hillary) 22.95%
10% of the remaining 19.5% who are Democrats 1.95%
total 33.3%
the surplus-- these total out to
Hillary will get about
9% of the remaining who are independents 3.6%
90% of the remaining 19.5% of Dems after Bernie 17.55%
10% of remaining Republicans after Bernie 2.55%
total 23.70
Even if you take away 10% from my estimates for Bernie, and give them to Trump and Clinton, Bernie still wins.
I'll throw in another game changer. What if Elizabeth Warren runs as Bernie's VP and Bernie promises to step down after one term so she can run in four years? If not Warren, Bernie will come up with a GREAT VP. (If he runs as a Green, I don't think Jill Stein, though I respect her and voted for her in 2012, would be the best VP choice.)
Bottom line, I'd rather click on a Sanders green party option on the ballot than write him in. Or better, if the buzz about Bernie going thrird party really builds, it may scare the Democratic establishment enough so the superdelegates into sanity, so they make Bernie the Democratic choice.