Slater served as state Election Board secretary from 1971 to 1988. Since that time, he has served as legal adviser to the state Senate. He is also co-owner of Campaign Technology Professionals LLC, a campaign finance reporting firm.
The 69-year-old Slater has represented a number of clients who have appeared before the Ethics Commission, as well as candidates and groups involved in election court cases. In 2010, he testified before the House Rules Committee that the Ethics Commission legally could not issue reprimands to candidates accused of violating ethics rules.
He was also the registered agent and attorney for A Better Oklahoma City Inc., a nonprofit that received money through the Greater Oklahoma City Chamber of Commerces Forward IV program and, in turn, funded an independent expenditure group called Committee for Oklahoma City Momentum.
The Momentum group was a major player in the 2011 Oklahoma City Council elections, in which a record amount of independent expenditures was spent to support or unseat candidates under loosened campaign donation restrictions.