If Cornyn can be kept under 50%, he’s beatable in the runoff.
I do not believe he has any chance if it comes to a run off.
http://www.texasgop.org/elections/candidates/#United States Senator
In a non-presidential election year, the typical primary voter is a little more tuned in to the specifics than the average voter.
This household won’t be sending any votes Cornyn’s way.