Texas has a pretty strong democratic heritage. As late as 10 years ago, the state assembly had a democratic majority and 17 of the 30 congressional seats were democratic held. I still believe that a democrat could win a statewide election in Texas but it has to be more of a Lloyd Bentsen type as opposed to a Barbara Boxer type.
^^^^
This.
It is important to remember that although Obama overperformed in the cities he still lost the election in Texas by 12 points in a nationwide environment very favorable to Democrats. Hell Clinton got a lot closer in 1992 and 1996 than Obama did with a third party candidate running.