I agree. Bill O’Reilly (and perhaps others) is already floating the theory that Cruz will offer Kasich the VP slot well before the convention, locking in his 143 delegates and narrowing the gap between him and Trump.
If Trump were to accept Liddle Marco (”who is actually a nice guy”) it would neutralize Cruz’s move and make it much easier to get 1237 regardless of California.
Probably not Trumps #1 choice, but “it’s business”. Rubio has served in the Senate and he was the speaker of the Florida House, so he has the legislative expertize Trump has said he would want. He’s also young, Hispanic, and has a different personality type that could offset Trump’s style. Trump would win Florida without him, whereas Kasich as VP would be a plus in swing-state Ohio.
Ironically this means the #3 and #4 candidates have a lot more power than they deserve!
There is no locking possible.
Delegates have their own minds, especially after the first ballot. But, candidates can speak their minds, and suggest who they want their support to go.
That said, if Kasich "releases" his delegates to vote Cruz, they'll almost all vote Cruz. If Kasich "releases" his delegates to vote Trump, some of them... I think... might vote Trump.