Tex. Elec. Code § 204.005
If a vacancy occurs during an odd-numbered year or after the 62nd day before general primary election day in an even-numbered year, the remainder of the unexpired term shall be filled by a special election in the same manner as provided by Chapter 203 for the legislature, except that:
Acts 1985, 69th Leg., ch. 211, Sec. 1, eff. Jan. 1, 1986.
Amended by Acts 1986, 69th Leg., 3rd C.S., ch. 14, Sec. 30, eff. Sept. 1, 1987.