I believe that the chance that Rump will out and out quit the race, unexpectedly, are higher than his supporters might realize
Reasoning:
1) Campaigning is expensive
2) Trump's speed is "full tilt retarded" as Frank Cannon brilliantly put it.
3) At some point even Trump has to realize he's not cut out for this
4) Lots of whispers that Trump ain't really in it to win it. Just wanted second place to feed his ego.
But really of all the above #1 is biggest reason Trump will unexpectantly quit at some point. He just loves money too much to waste on this crap.