In an increasingly testy Republican runoff for railroad commissioner, state Rep. Wayne Christian is reaching into Gary Gates' legal history in an effort to paint his opponent as a “slumlord.” Gates, who has relentlessly criticized Christian's record as a lawmaker and brands him a “career politician,” calls the attacks dirty politics. Regardless, the issue highlights the vulnerabilities of a candidate who earned his wealth by building a small real estate empire of relatively low-cost rental units.