That was largely due to Dubya White House and Tokyo Rove doing their damndest to stop Conservative Rep. Ed Bryant. Bryant was of modest means and they used huge amounts of $$ to buy the seat out from under the choice of the party base.
The base is pretty hopping mad that they’ve been shut out and denied a real Conservative for so long, but they’ve got to coalesce behind a single candidate this time. A split field on the right with Haslam on the left is the worst thing that can happen. But we absolutely have got to get closed primaries and runoffs, something the establishment viscerally opposes.
That seems to be the key, a single conservative vs the weasel.