Simply put, Hutchinson, in order to win, will have to pull a McCain here and rely on the support independents and Democrats, as Texas has an open primary system, where any registered voter can vote in any one primary he or she wishes to.
I doubt that Democrat voters will vote in a Republican primary. If there is an opening in the Senate, I would expect a contest for the Democrat nomination, as I don't see any Republican statewide office-holder switching positions at the last moment into a senate race. And Democrats aren't accustomed to switching to the Republican primary because there is nothing happening in their own primary. This is unlike the reverse position 20 years ago, where in much of the state, if you didn't vote in the Democrat primary, you had no vote in local and legislative races.
So what KBH needs to do is draw people who don't typically vote in primaries (turnout in the general election has been 3 to 4 times the combined vote in the primaries). What might help is if Strayhorn runs for Lt. Governor. Voters in general are not as conservative as the people who go through to the convention. Since the primary is so early and open to all independent voters, candidates do not have to necessarily appeal to the hard core activists (unless they need funds).
Carole Keeton Strayhorn (she remarried last year). I don't think she has the resources to run against Perry or Hutchison. If Strayhorn moves it will be for Lt. Governor. This would probably help Hutchison as it would provide another race to interest voters.
He has the advantage of being able to prepare to jump into the Senate race, but if Hutchison stays, he easily wins re-election in his House seat.
Sharp has been out of office for 7 years, and lost 2 statewide races. People might not remember him. The Democrats are going after Cuellar, so I'd expect him to be concentrating on holding that seat. If Cuellar ever holds statewide office, it will be as a Republican.