It is the changing dynamics of the presidential general election ... that may well be pushing Cruz toward at least a pro forma gesture toward his party’s nominee. By that I do not mean that Cruz is gaming the possibility that Trump will win; no matter what he does now, the Texan will almost certainly be frozen out of any real influence in a Trump administration. It’s the significant likelihood of a narrow Trump loss that is probably bugging Cruz and his advisers. It was one thing to stay on the sidelines and watch sadly as Trump self-destructed and lost by a landslide, as appeared likely for a good part of the general-election campaign. In that scenario, Cruz was in a good position to help pick up the pieces afterward and become the chief advocate for a movement-conservative version of the GOP’s post-Trump future. But after an agonizingly close Trump defeat, Cruz would become a prime object of recriminations for having helped Hillary Clinton and her baby-killing, Christian-hating secular-socialist minions to seize power.Also, please note that Cruz's favorable ratings among Republicans began plummeting as soon as he took on Trump in the later stages of primaries, and as a result of his opposition he's looking at the possibility of a well-financed primary challenger in 2018.
So does this mean that Trumpism is now the undisputed ideology of the Republican Party? Not really.
The Republican Party has the same ideology it's had for years, one that can be summed up in one sentence: Democrats are the Antichrist. Foolish pundits, and even politicians like Cruz, think there's more to Republicanism than that, but there isn't. Trumpism is dominant right now because Trump seems like the person who can most effectively cause pain to Democrats, and to the right's other enemies (non-whites, non-conservative women, gay people, climate scientists, etc.).
Cruz probably thought Trump would lose badly, after which Wingnuttia would conclude that the loss was because Trump was really a filthy liberal; at that point, Cruz could pose as the "true conservative" savior for 2020. But Trump, even if he doesn't win, is causing the right's enemies conniption fits, so he's the strong horse the right likes at this moment, and everyone on the right needs to get behind him. Right now it looks as if Trump will lose a close one -- I'm not sure Cruz endorsed early enough to completely avoid partial blame for that, but if he'd never endorsed, his share of the blame, according to the conservative base, would be right up there with ACORN's.
Trump will probably quit politics if he loses, so there'll be a new battle for who makes the right's enemies the most miserable. Cruz is going to have a hard time regaining the trust of the faithful, but he's going to try, and he wouldn't have had a chance otherwise.
I think he really thought there'd be a post-November ideological battle, when, really, all there'll be is a contest for who can be nastiest to Democrats. He might regain his mojo and have a shot at pulling that off. It's certainly in his nature.