Where are they polling Austin?
Cruz barely beat O’Rourke, especially by the standards of recent Texas electoral history. It is true that it was a bad year for Republicans in general, but so too was 2012 and Cruz won easily that year.
Of course the media will seek out and champion such polls as these in order to try and give them a self fulfilling effect, but the sad and unfortunate truth is that Texas will become less red going forward. Decades of mass immigration (legal mostly, but also illegal) have created a more Democrat-friendly population and now electorate in Texas. Maybe the results of 2018 will light a fire under thr party’s rear end help restore order in the next few cycles, but it’s almost inevitable that Texas will become a battleground state.
So long as white Texans keep voting overwhelmingly for the GOP then a collapse like has happened in California is unlikely, but dominance will end. If whites moving to Texas are at all similar to those who have moved into states like North Carolina, Georgia, Florida, et al, (ie liberals fleeing blue state governance who then continue voting Democrat in their new home) then it’ll be even worse.