Texans appear to feel strongly about this topic.
It's an anti-gay marriage amendment. I guess this proves that even big cities in Texas (excluding Austin) are very conservative.
It's not just Texas. Take a look at the map of the 2004 gay marriage amendment in Ohio:
That red county is Athens, which contains Ohio University, and is decidedly liberal and has a relatively smaller population.
Although Cleveland, Columbus, Cincinnati, Toledo, Akron and Dayton might have voted for the amendment by smaller margins than the rural areas, they still did so nonetheless.