Republican Richard Ackerman and Democrat Shirley Hafner were the early leaders in the primary race for the Assembly seat in north Orange County's 72nd District. With two-thirds of the votes counted, Hafner, 56, an administrator at UC Irvine Medical Center, and Ackerman, 52, an attorney and former Fullerton City Council member, were headed for a runoff Sept. 12. Two other Republicans, Chris Norby, 45, a Fullerton City Council member, and Barbara Kiley, 48, a member of the Yorba Linda City Council, trailed Ackerman. Hafner was the only Democrat in the race. The unusual July special election was a result of recent term limit legislation that forced Ross Johnson, an assemblyman from the 72nd District for 16 years, to step down or seek another office. Johnson moved his home from Placentia to Irvine and was elected to the state Senate in May in the 35th District.