He just created a #NeverCruz movement and ensured he will never have a shot at winning a GOP nomination in the future. Mr Trump quite graciously offered him a key speaking slot and the chance to keep his pledge to support the nominee. Cruz, ungraciously, failed to keep his word. Two effects....in the short run this helps Trump significantly with Republicans very few of whom can stand Cruz, particularly now that he's demonstrated his lack of courage and class.
Second, in the long term, you can simply take Cruz out of the 2020 equation as he will now be shunned by most voters in the GOP. The hard core Cruzies will stay with him, but that 10% isn't enough to get him anywhere significant. Teds pettiness has finally caught up to him, and exposed his selfish character. Sad, really.
Cruz was supporting the nominee by being there and making a case against Hillary. I find it insulting that Trump would even expect an formal endorsement after the smear campaign he ran against Cruz and his family.
And then there is this:
In fact, the source added, a few hours before the speech, the Trump campaign had been in negotiations with Cruz for Cruz to play a larger role in the campaign, including advising on Israel policy. Minutes after the speech ended, the source noted, the Trump campaign instantly informed them that the offer had been withdrawn.
http://www.dailywire.com/news/7665/exclusive-cruz-camp-trump-campaign-approved-speech-ben-shapiro