In this paper, we investigate the interaction between two firms, which are involved in a repeated procurement relationship modeled as a multiple criteria auction, and an auctioneer (a government employee) who has discretion in devising the selection criteria. Our main result is that favoritism substantially facilitates collusion. It increases the gains from collusion and contributes to solving basic implementation problems for a cartel of bidders operating in a stochastically changing environment. A most simple allocation rule where firms take turns in winning, independently of stochastic social preferences and firms' costs, achieves full cartel efficiency (including price, production, and design efficiency). In each period the selection cr...