A vote for Cruz or Kasich is a vote for a “contested convention”. Cruz people believe that he can manipulate the process enough to get the nomination on a later vote. I doubt whether this is possible; I think that it is likely that his belief has been reinforced by the party elite who feel they will be able to manipulate the convention enough to get whoever it is they really want in place... probably Ryan. Whoever it is would lose, but they are OK with that as long as they get to keep their positions.
Here’s the one Trump made last night;
https://www.youtube.com/watch?v=jxLwDfQzybs&feature=player_detailpage#t=145