Original sentence: " Unseating an incumbent supervisor is extraordinarily difficult, due largely to the prohibitive difficulty of mounting a successful challenge in districts of such enormous geographical and population size.Each supervisor has a budget of $3,000,000 for staff and office expenses, with the remainder going into a "discretionary fund" that can be used for grants to non-profit agencies, without a vote by the other supervisors.Supervisors routinely waive parking and rental fees for various organizations, provide bus trips and give free tickets to county facilities to constituents, and build projects for the community with the supervisor's name clearly marked
Edited sentence: " Unseating an incumbent supervisor is extraordinarily difficult, due largely to the prohibitive difficulty of mounting a successful challenge in districts of such enormous size (comprising roughly two million constituents each)