Cruz said it himself that a thumbs down on any trade proposals would be available to Congress.
The secrecy of certain elements of the trade deal are an issue but Cruz has the power and influence to bring such elements to daylight and then file amendments to negate any deleterious provisions.
Ted Cruz is seeing the bigger picture and the process. The Trade Deal is not written in stone yet so Ted Cruz sees the ‘process’ as editing the deal to benefit him as President and thereby benefit America and Americans; simple as that.
Here’s what Ted has to say directly about your question on this (start time 52:00):
https://www.youtube.com/watch?v=sznh5AjageI
Cruz is blowing smoke. Period.