In 1983, Mattox was indicted for
commercial bribery and prosecuted by
Travis County District Attorney Ronnie Earle, a Democrat close to the late Governor
Ann Richards. Earle later prosecuted the Republican congressional leader
Tom DeLay. Like the DeLay prosecution, the political background of the Mattox prosecution related to an attempt to conceal the delivery of corporate funds to an election campaign. Mattox had received a campaign contribution of $125,000 from his sister Janice, a Dallas lawyer. Janice Mattox, in turn, had obtained a similar amount from Seafirst Bank in
Seattle, which had close ties to Mattox supporter
Clinton Manges, a controversial
South Texas rancher-oilman who was the successor to
George Parr, the corrupt "Duke of
Duval". Manges was co-
plaintiff with the state (represented by Mattox) in major litigation against
Mobil Oil Company. Mobil had attempted to depose Janice Mattox concerning the Seafirst transaction, which led Mattox to threaten Mobil's law firm,
Fulbright & Jaworski, with loss of its tax-exempt bond practice, a power held by the attorney general in Texas. Secretly recorded by the recipient of the threats, Mattox did not deny threatening the law firm, nor did he deny the Seafirst transactions, his defense being based on the legal definition of the crime of "commercial bribery". After a long trial, Mattox was acquitted. His aggressive attacks on alleged wrongdoing by corporations gained him considerable popular support. In 1989, Mattox was inducted into the Woodrow Wilson High School Hall of Fame. ==Challenging Ann Richards, 1990==