Tex. Transp. Code § 392.036
It is a defense to prosecution or suit for a violation under this chapter if at the time of the alleged violation the defendant is a candidate for elective public office and the sign is placed:
Acts 1995, 74th Leg., ch. 165, Sec. 1, eff. Sept. 1, 1995.
Acts 2007, 80th Leg., R.S., Ch. 612 (H.B. 413), Sec. 3, eff. September 1, 2007.