He won't be able to get on the ballot in Texas no matter what. See here: uselectionatlas.org/FORUM/index.php?topic=232226.0
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Texas and South Dakota have "sore loser" laws which prohibit a candidate who has lost a major party's nomination for the presidency to run for president as an independent. Of 45 states with similar books on the laws, these are the only two states which appear to apply to presidential candidates. This takes 41 electoral votes out of play for Trump.
But that means he can still collect the signatures for TX until May 9, because the GOP convention is ... after that deadline. Which means Trump technically has not "lost" the GOP nomination yet at the time of the TX deadline.
Or does the "sore loser" law apply to the TX GOP primary results ?