To hold office in Texas, you must acknowledge the existence of a supreme being:
Here's the actual language of the Texas Constitution:
Sec. 4. RELIGIOUS TESTS. No religious test shall ever be required as a qualification to any office, or public trust, in this State; nor shall any one be excluded from holding office on account of his religious sentiments, provided he acknowledge the existence of a Supreme Being.
Quick Quiz: Which one of these is a Supreme Being in Texas?