Let me also add, that a fractured base from a contested convention is easier to repair than a fractured base from hateful rhetoric heaped onto supporters of one candidate by supporters of another candidate. Both Cruz and Trump supporters are extremely guilty of this, but Trump is the CANDIDATE who bears the blame by setting the example and legitimizing it.
Trump used "The other guy started it" as a way to justify his own bad behavior. That wasn't always a true statement, but even if it was, Trump admits he hits back harder. And what Trump does is often completely out of proportion to what was done to him. It's comparable to using a nuclear attack in response to a poke in the side.
I don't agree with a lot of Trump's "policies", but even if I agreed with him 100% I could never support a person like him, and would only ever vote for him if I was in a situation where my vote for him could help prevent an equally despicable person with even worse policies from winning.
Since I live in California, I can take pleasure in voting against Trump in the primary where my vote could actually matter for the first time in my lifetime, and I can take pleasure in not voting for Trump in the General, where my vote doesn't matter because the Democratic nominee will win the state by millions of votes.
Ironically, going into the campaign, I was a Trump fan and he was my first choice. It was observing his poor behavior and hearing his poor answers to substantive questions that has made me firmly opposed to him.