I disagree. If the “tea party” movement, for example, had been for real and state conventions of tea party members were held to nominate their GOP slates, enough of a force could be built to either take over or splinter and then replace the GOP IMO.
It would probably be a decade-long project, however.
It’s hard to compete with their money and resources I think.
That’s why I suggest Cornyn as a prime target. The fish rots from the head.