Although Mr. Rubio is the obvious establishment favorite, leading Mr. Kasich in national polls, prediction markets and delegate math, the two are splitting some votes. To have his best chance against Donald Trump and Ted Cruz, Mr. Rubio needs Mr. Kasich to drop out. The longer both candidates remain in the race, the worse it is for both of them. It’s safe to assume neither would like to see Mr. Trump get the nomination.
So Rubio and Kasich would like the other to drop out ("swerve") while they contest the nomination ("go straight"), and each would hate to see Trump win the nomination (they "crash" if each goes "straight"). And both dropping out would likely lead to a Trump victory.
Here are three obvious strategies: commitments, promises, and threats. Here is the obvious promise:
...Mr. Rubio could offer Mr. Kasich [to pick him as a running mate] in exchange for dropping out — provided he becomes the nominee, of course. (A simple Google search of “Rubio Kasich side deals” produces no shortage of opinions on the matter.)