Although Texas showed strong growth in the last census, only about 10%-11% of that growth was among Whites. The other 89% to 90% was growth among the minority population -- primarily among Hispanics (but Blacks also showed a larger percentage of growth than Whites). And there is nothing to signal that the same thing won't be true when the 2020 census is taken. Note that the median age of Whites in Texas is 41, while for Blacks it is 32 and for Hispanics it is 27. This means a much larger portion of Whites are older citizens -- and when the older citizens die off, the state will have a larger minority percentage of the population.
Hispanics already make up 38% of the Texas population, and when you add in Blacks (about 11.8%), Asians (about 3.8%), and other races/ethnicities, you can see that Texas Whites already make up less than half of the state's population (about 45%). Whites still make up the largest percentage of voters by far, but how long can that last with the minority population growing much faster than the White population every year? Texas Democrats have already started a statewide campaign to get more minority voters registered, especially Hispanics.
Note also that Hispanics currently make up 48% of the school population in Texas, and 50% of all births in the state are to Hispanics. There is no doubt that the day is coming when the Texas population will be predominantly Hispanic, and they will make up the largest segment of voters in the state. It is no longer a question of if it will happen, but how long it will take to happen.
This is scaring the hell out of the Texas Republicans. They saw that in the last presidential election more than 70% of every minority group voted Democratic, including Hispanics. And it should scare them, because they have pursued (and still pursue) anti-minority and anti-immigrant policies -- policies sure to hurt them in the future.
They could take a reasonable road, and change their policies to please the coming Hispanic majority. Hispanics have shown in the past that they are willing to vote Republican when it seems to be in their interest. It would make a lot of sense to alter their policies, especially in a state with the demographics that Texas is showing.
But the Texas Republican Party is controlled by the racists, teabaggers, and fundamentalists -- and those groups are not ready to give up their world of White privilege. And the politicians they elect are bowing to their wishes. So instead of moderating their ultra-right racist policies, the Texas Republicans have opted for a different path. They are opposing immigrant reform, convinced that giving immigrants citizenship will just create more Democratic voters -- overlooking the fact that 70% of Texas Hispanics were born in the U.S. (and most of the children of the other 30% will also be born here). And those people will vote Democratic because of the anti-Hispanic Republican policies.
They are also trying to suppress the vote of minorities through measures like Voter ID laws and the gerrymandering of districts. But while this kind of action might delay their demise by a few years, they cannot succeed in the long run. Someday that will be overwhelmed by sheer numbers.
The future does look bleak for Republicans in Texas. But the crazy thing is that it didn't have to be that way. They are bringing it on themselves by the vicious and mean-spirited anti-immigrant and anti-minority policies they love so much (not to mention the anti-woman policies). In effect, they are engaging in a massive political suicide.
(The charts above were made with information from the Pew Research Center, who gleaned it from the most recent American Community Survey.)