  We propose a novel method to search for the chiral magnetic effect (CME) in
heavy ion collisions. We argue that the relative strength of the magnetic field
(mainly from spectator protons and responsible for the CME) with respect to the
reaction plane and the participant plane is opposite to that of the elliptic
flow background arising from the fluctuating participant geometry. This
opposite behavior in a single collision system, hence with small systematic
uncertainties, can be exploited to extract the possible CME signal from the
flow background. The method is applied to the existing data at RHIC, the
outcome of which is discussed.
