Like many Texas Republicans, Strayhorn didn't convert to the Republican Party until the party became competitive in Texas.
That's also true of Perry.
Hoping for a better candidate, but few wish to challenge a sitting governor, and in Texas, statewide recognition is pretty much impossible without holding a statewide office.
. . . and also true of great public servants like Phil Gramm and Ralph Hall. The thing is Perry, Hall and Gramm acted like Republicans before and after the switch. Strayhorn is liberal through and through.