It'd probably be something like 20% Sanders, 30% Democratic Party (A lot of people just vote for the democratic party instead of who they actually want), 40% Republican Party and 10% other third party. Annoying Orange is guaranteed the victory if Sanders runs third party, which is exactly why he's never going to do it.
even then i guess Annoying Orange wouldn't
necessarily win, nobody would have a majority. it'd be turned over to the house of reps where each state gets one vote
and uhhhhh

well i guess the republicans would probably win most of the time in that situation (out-of-date map, but the trend stays the same, most states tend to be republican, but a large part of the population is concentrated in blue states)