The chairman is the politician among the oligarchs. He influences parliament and can thus manipulate votes.
How this is played: The chairman has his effect in phase III. He may add one vote to each vote. For example, he may turn a 3:2 into a 3:3. He may also decide in the event of a tie in legislative votes. If he cannot or does not want to make use of these effects, he may draw a bribe in IV.