We investigate how possible collusion, interpreted as a positive prior probability that collusion may occur, influences equilibrium prices in states of the world in which collusion, in fact, does not occur. We explore the mechanism in a theoretical model of consumer search, based on the Stahl (1989) framework, and show that with possible collusion, equilibrium prices are higher even in the absence of collusion. We test the model predictions in a series of laboratory experiments. The results are qualitatively consistent with our theoretical predictions.