I don't think Cruz's national aspirations are dead, but the 2016 campaign did erode his credibility. Voters like candidates with a consistent message that is easy to categorize, and Cruz's waffling and indecisiveness in his approach to Trump muddied his previously untouchable credentials.
He initially opposed Trump's Muslim registry, claiming that he "didn't like government registries of U.S. citizens." As the Trump campaign gathered steam he pulled a full 180 and backed heavy policing of Muslim neighborhoods. He made a high-profile point of refusing to endorse Trump, and then proceeded to do it anyways. He claimed the moral and religious high ground, yet later endorsed and campaigned for a man who isn't even biblically literate and has been married three times. Some politicians can get away with flip-flopping, but not a guy whose entire brand was built on his bulletproof, uncompromising conservative principles.
In short, yes.
If he loses to Beto O’Rourke in November as he is now leading by only 3 percentage points, his aspirations will be likely to die.
