The explanation asked for is why would Arpaio endorse Perry?
Oh, good point, why would a tough on immigration sherrif endorse an open borders guy? Beats me, maybe sherrif’s are appointed down there and he doesn’t want to mess up a good thing?
It’s probably that “stupid texas thing”, here’s the best explanation I can find ...
http://www.youtube.com/watch?v=QltlctqfY4E