If I were a Republican, I'd support Hutchison simply because she can't lose in the general.
Yes, this should be an important consideration, especially since Texas is gaining all those House seats in 2012. However, Perry seems to be doing well against White in polls too (not quite as good as KBH though). One thing that bothers me is this - does Perry really deserve to be a Governor for 14 years? That's a long, long time. Another thing working for Kay in my mind is that this way her Senate seat would be open and some fresh faces would have a chance.
Speaking of fresh faces, apparently Debra Medina has done a great job in the Republican debate and is scoring about 15% in polls. So the race is not just Perry v. Hutchison.
My prediction is that Perry stili manages to takes this, given that he's the most socially conservative candidate and Republican primaries in Texas are dominated by social conservatives.