This is a sentiment I've often seen on this forum and online, and I haven't gotten a very satisfying answer.
The main argument I see is that the GOP will continue to gain in rural TX and with Hispanics. The issue with this argument is that this is literally what happened in 2020 but it didn't stop TX from shifting and trending left. And infact many of the massive R swings we saw with Hispanics in places like South Texas are going to be hard to replicate cycle after cycle because you'll very quickly reach a ceiling.
The reality is over 2/3rds of Texans live in one of the 4 main metro areas (Dallas, Houston, Austin, and San Antonio) all of which have had pretty clear and consistent leftwards shifts for the past 2 decades; even if the GOP gains more ground elsewhere these places will always win out. Any path to keeping the state GOP leaning in the long run has to run through the GOP holding their ground in these metro areas.
The GOP almost achieved this in Houston metro in 2020 thanks to massive gains with urban Hispanics and some other ethnic minorities in places like Alief, but even then Harris County and Houston metro as a whole still swung left.
Another problem for the GOP is just growth. The fastest growing area of the state is metro Austin which is also the most liberal, and only getting bluer by the cycle; heck Beto 2022 outran Biden 2020 in Travis and Hays Counties! In the other 3 major metros, there is a strong correlation between the fastest growing suburbs and strongest democratic shifts. On the flip side, most of the deepest red rural Texas Counties are stagnant or outright shrinking.
So why is the GOP suddenly going to be able to make the state stall out? Massive and consistent gains with non-white voters? Transplants becoming more R-favorable? They manage to stop the bleeding with suburbanites post Trump? Genuinely curious.
While I'd point out swings in much of the Houston area were underwhelming in 2020, a bigger factor to point out is that rural TX, outside of maybe the RGV, is quite literally maxed out for the GOP. They've broken 80% in the clear majority, and 90% in quite a few - there's simply not much room left for them to expand their margin in the vast majority of rural TX.
And all the mid-sized towns in TX (like Waco and Lubbock) already vote quite a bit to the right of where they "should."
