Saving a corporation from an Arthur Andersen–style meltdown ain’t enough to secure a CEO’s job these days. So Michael Cherkasky is stepping down from troubled insurance conglomerate Marsh & McLennan Cos., which he helped avoid incurring criminal charges for alleged bid-rigging in its insurance brokering business. The former prosecutor struck an $850 million settlement in 2005 with then–New York attorney general Eliot Spitzer. But Cherkasky couldn’t overcome the weak performance of MMC’s core risk and insurance business, which ran a 4.9 percent operating margin in the quarter ended September 30, versus rivals’ high-teens margins. Under Cherkasky’s three-year reign, said nonexecutive chairman Stephen Hardis , “MMC’s financial performance has fallen far short of our expectations.” Cherkasky was not available for comment.