Nueces County District Attorney Mark Gonzalez, a Democrat, announced his resignation in a Sept. 5 letter to Texas Gov. Greg Abbott, a Republican, who will name his replacement.

At the same time, Mr. Gonzalez announced a run for U.S. Senate to unseat Republican Senator Ted Cruz, according to local media.

Mr. Gonzalez sidestepped a civil lawsuit scheduled in December to remove him from office for "incompetence and official misconduct under the guise of prosecutorial discretion" and failure to give bond.

The lawsuit claimed Mr. Gonzalez "nullified" the law, abused his authority, and violated his oath to preserve, protect, and defend the Constitutions and laws of the United States and Texas.