Technically the rules for this convention have yet to be written, but last years rules are the starting point. If those rules change it will be done a few days before the convention by the delegates on the rules committee. That means Cruz/Trump will essentially write the rules if they stay aligned.
We haven't had a real contested convention in awhile, but many states require their delegates to vote a certain way regardless of any deals made. In Iowa, for instance, as a result of going first we HAVE to vote at the convention, how the vote was in the state, regardless if another candidate says to use his delegate to vote a certain way. The only exception is if one candidate is clearly the winner, we are allowed to vote 100% for that candidates. Like Romney last time.
So if Trump & Rubio come to the convention as a team, in many states that would not be recognized until the second ballot under the current rules. Again that could change is a few months as alliances could be formed.
As for the GOP not just giving it to Trump because he is so close, I will list their concerns. You can call me stupid, I am not even saying I agree with these, I am saying this is their concerns
1) Trump would suffer a major blowout in Nov. He has 70% of America viewing him negatively. And the negative feelings are personal rather than political, which are harder to change perceptions.
2) He has no state organizations. To win swing states, Ohio, Florida ie you need to be working these for a long time. After both these states primaries, Trump pulled completely out. Cruz still has a number of people working in these states.
3) Trump has no fund raising to date. He self financed his own race to date, but has said he won't fund the general. That will take $1B from private and SuperPacs combined. To create a donor list willing to max out at $2700 each takes time and he will need that in the next few months. The big money SuperPac guys don't really like him, so he will be grossly underfunded.
4) He is really not a conservative and the GOP is a conservative party.
I know a lot of people will scream GOPe et al, but if it is not Trump it will be Cruz, and the GOPe HATE Cruz. Hate him.
I really think the last thing is Trump attacked other candidates so personally, they are really not going to coalesce around him. Look at Rubio, he is working with Cruz in AR to get a slate of delegates that will vote for Cruz on second ballot and not Trump. Rubio is out, why is he working with Cruz and not Trump? Because I really think there is a strong dislike towards Trump from many of the other candidates.
Thank you, but I must admit I don't know enough about the process to engage anyone in a debate about it. I am merely trying to understand it better. Some of my questions might be smart enough to pass for debate...others might be plain dumb questions. :)