And if you want them to get out from democraty, declare war on them, make an alliance with another a.i., 15 turn later, ask your ally for a trade embargo against them ( this will cut luxuries trade for another 20 turn and create unhappiness and it will cost you nothing), keep the war on until they collapse into monarchy or communist. To avoid war wearniess, increase your lux slider to 20 % and buy luxuries from your ally. sooner or later they will collapse, especially if you raze 2-3 of their city ( increase their war weariness).