A controlled opposition is a protest movement that is actually being led by government agents. Nearly all governments in history have employed this technique to trick and subdue their adversaries. Notably Vladimir Lenin who said ''"The best way to control the opposition is to lead it ourselves."
Count Mirabeau was part of the controlled opposition, because although everyone thought he was supporting the revolution, in reality he supported the monarchy and was a personal friend of the king. He was a government agent.