He is giving up his seat. Probably to dedicate himself full-time to the Dominionist Christian world he wants to build.
This is a nice quote to remember our Tom by:
Asked if he had done anything illegal or immoral in public office, DeLay replied curtly, "No." Asked if he'd done anything immoral, he said with a laugh, "We're all sinners." Asked what he would do differently, he said, "Nothing."
Now that's admirable. I could name a zillion things I'd do differently in my past. But then I'm not a wingnut.