Brendan Reilly said he'll run as a Democrat for Cook County Board president in 2026. His campaign sets up a potential showdown with longtime incumbent Cook County Board President Toni Preckwinkle. Brendan Reilly announced on Wednesday that he will run for Cook County Board president as a Democrat in 2026. The alderman’s announcement sets up a potential matchup with longtime current County President Toni Preckwinkle in the Democratic primary. "I am running for County Board President because Cook County government is broken and is long overdue for change," Reilly said in a statement.