It's all legal, and if a majority of delegates agree, there is no way to stop it. Here's how it could happen.
Effectively, we'll know which way this will go Monday night with the vote on adopting the rules. If the rules are adopted as the Rules Committee sends them to the floor, it's all over. But if the convention votes to adopt a minority report inserting a "conscience clause" allowing delegates to vote for whom they will, there is probably a better than fifty-fifty chance that somebody other than Trump will emerge from Cleveland as the nominee.
Though the Trumpsters continue to try to confuse the issue, the Supreme Court ruled long ago that state laws requiring delegates to vote a certain way even on the first ballot are unconstitutional. The SCOTUS decision in Democratic Party v. Wisconsin ex rel LaFollette in 1981 was just reinforced by a district court ruling in Virginia as reported by this blog.
So it's all a matter of what the delegates themselves decide to do. Conventions have traditionally been deliberative bodies which themselves chose the nominees with only advice from the primary voters- and before the present primary-driven system was adopted in 1972 unquestionably did a much better job of it than the rank-and-file have since (if you doubt that, take a look at the quality of the nominees before and after 1972!). Moreover, the argument that it would be undemocratic if the convention were to select somebody other than Trump runs afoul of two basic facts. The first is that Trump only received the votes of slightly more than a third of the Republican primary voters- and there can be no doubt that the majority of the voters preferred somebody other than Trump. They voted for somebody other than Trump! Secondly, the very strong likelihood is that a majority of the primary voters would have preferred almost anybody other than Trump. Trump's nomination would be a triumph of a plurality over the majority.
All hell will break loose if Trump is denied the nomination. But it is the only possible way for the Republican party to either remain true to its historic principles or to have a snowball's chance in the nether regions of winning in November.
Pray for the minority report and the NeverTrumpers. If they fail, we get Hillary Clinton as our president for the next four years.
Graphic by DonkeyHotey