AUSTIN—Travis County District Attorney Ronnie Earle on Friday announced he won’t seek re-election next year. The 65-year-old Democrat was at the center of the criminal investigation of Republican former U.S. House Majority Leader Tom DeLay. DeLay quit Congress last year. Earle’s term has one year remaining, and his resignation will bring to an end to his three-decade reign in which he battled some of the biggest names in Texas politics. Earle has been criticized by DeLay and other Republicans, who say some of his prosecutions of elected leaders are politically motivated. "This is a no-brainer for him. He never had...