Abstract: Briefly, the present invention relates to a molded case circuit breaker. The molded case circuit breaker includes at least one pair of separable main contacts, mounted on upper and lower contact arms. One end of the lower contact arm is formed as a U-shaped portion defining depending leg portions and a bight portion forming a reverse current loop. Disposed adjacent the lower main contact on the lower contact arm is an arc runner assembly which directs the arc resulting from a separation from the upper and lower main contacts into an arc chute to quench the arc. The arc runner assembly includes an arc runner and a support block. The arc runner may be formed from steel and is carried by the support block, disposed between depending leg portions of the lower contact arm. The support block is formed from an electrically insulating material, such as a glass polyester.