I, like duke, use the tribute function to provoke war when I can't attack due to governmental reasons. Usually I have good success employing this strategy.
I remember one game however when I was trying to get the Spanish of declare war, and was demanding tribute every turn. Every turn they would give me 25 gold, smile and wave. After about 10 turns I was getting tired of waiting for them to declare war, I had all my military units lined up at the border ready to go. But they just kept shelling out 25 gold each turn. Demanding that they withdraw their troops didn't work either so I was forced to take their money and finance a war against the Russians instead. I returned later with a different govt and blew the Spanish to pieces.