Here’s what a Hutchison hand told me. (I was driving and talking on my cell phone, so this is the gist of the conversation, not a verbatim rendition.)
This is a legislative session in which Perry needs to show that he is a leader who can bring people together and accomplish positive things for the state. But the letter makes him appear as a politically motivated, small-minded pol. What kind of message does this send to people who are willing to give their time and their effort to public service?
Here’s another item I heard: Dewhurst is trying to distance himself from the letter, presumably in conversations with Rowling.