Florida Democrats are coming off one of their worst election cycles since Republicans took control of the legislative and executive branches more than two decades ago. But as potential candidates weigh runs for higher office, Democrats are staring at a tumultuous primary season that’s grown more complicated by the threat of redrawn congressional and legislative districts that favor Republicans, a fight they’ll wage in the Legislature next year with fewer members as some must resign to run in a special election for a congressional seat in January.