For the record: I am a Texan living in East Texas, I don't gamble (except for a Texas Lottery ticket a week) and don't care if we have casinos or not. I would not be interested in going to one.
There certainly is a "Bible Belt" mentality which will prove to be strong opposition.
But Texas is passing on a lot of revenue by not having casinos. There's a reason why Las Vegas and New Orleans have been top convention destinations, and it's not the climate.
A few casinos located in Galveston, Houston, Dallas, San Antonio, and one in the Rio Grande Valley (or South Padre Island) to attract the high-rollers from Mexico would generate a bunch of cash and keep Texan gamblers at home.