If Trump is within 100 or so delegates then Trump will make a deal with Rubio or Kasich to be the VP and take his 100+ delegates to obtain the nomination.
Kasich isn’t pretty and Rubio is a squirrel but if it gets the nomination it may be necessary
Fantasy/Hope
Then the demodogs will challenge Rubios eligibility and he will be forced to withdraw. Trump replaces Rubio with a better option
Rubio is out as of last night. Rubio essentially endorsed Cruz on Levin’s show.
Kasich has already expressed disdain for Trump.
But no doubt, Trump will be under massive pressure to do a deal with Kasich.