If U.S. politics is one interconnected system, why allow Tx to become blue?

Thst sums it up. Probably a third of registered Republicans are gutless low information slobs who dont have the stomach to do what needs to be done to prevent the invaders from taking over. Oh sure theyre happy to vote for tax cuts or maybe some extra defense spending but thats almost literally the extent of their conservatism when push comes to shove.