There was another poll out not long ago showing the same results if I remember correctly but can't remember who conducted it.
Strange things have happened with some powerful congress critters here in Texas.. Just a few miles to the East of this district was Jack Brooks who no one thought could be defeated and I remember watching him on tv at his campaign headquarters that night laughting it up. Until the western side of the district went against him and he was defeated by a no name Steve Stockman who got defeated the next election. That was in 1994 when the public purged some of the congress.
I really don't think DeLay will get defeated but then it has happened before when the populace decides it's time to throw the incumbent out.
The district is only marginally GOP, and becoming more marginal with time.