Your points are very well taken. To back up your comments, Rick Perry was the very 1st REPUBLICAN Lt.Governor elected in the state of Texas. Ever.
The issues are, how long did Perry continue to support the presidential candidates of the national Democrat party and its policies. When someone is still supporting a national Dim for president in 1988, there's quite a bit of political history that did not dissuade that individual away from the Dims prior to 1988.
And don't bother with claiming Perry voted for Reagan or GHWB. Any politician can claim anything that can't be proved one way or the other.
And don't bother with the history lessons about the transition of southern politicians away from the Dim party. I lived in Alabama through those years.