An elected official or government employee who is an idiot, is out of touch with reality, and has no idea what s/he is doing.
Running rampant in the halls of the senate are bureauclowns, many of whom have no legitimate reason to be engaged in public service.
Couple: That table is open.
Hostess: I'm sorry, that table is reserved for a group of lobbyists and congressional staffers.
Couple: Oh, so you serve bureauclowns here, huh? Can they at least agree on appetizers?