The new head of Marsh & McLennan Cos., Michael G. Cherkasky, has three key traits working in his favor: clean hands, a reputation for toughness and the right friends.

Unlike the bulk of Marsh's executive corps, Cherkasky, 54, is new to the company and has no connection to the insurance bid-rigging allegations and other scandals that have tarnished its three main divisions.

Cherkasky, the former chief executive of Kroll Inc., a risk management and security firm, joined Marsh & McLennan only this summer, when it completed its purchase of Kroll.

Before joining Kroll in 1994, he spent 16 years in public service, rising to become a chief prosecutor and head of investigations for longtime Manhattan District Attorney Robert M. Morgenthau.

"Mike is smart, he's tough, he's hardworking. He's got an outstanding reputation for probity," Morgenthau said. Marsh "had to put in a guy who can restore public confidence, and Mike's a guy who can do that."

While working for the district attorney, Cherkasky plucked a young Harvard-trained lawyer named Eliot L. Spitzer out of the rank and file and put him in charge of a complex investigation of the Mafia's influence on trucking in New York's garment district.

Now Spitzer is New York attorney general and Marsh is squarely in his sights -- his Oct. 14 civil fraud complaint against the company and refusal to negotiate with outgoing Marsh chief executive Jeffrey W. Greenberg led directly to Cherkasky's elevation.

Two people familiar with the process said the 10 independent board members of Marsh turned to Cherkasky because he was the closest thing to a clean outsider they could get without launching a full-fledged nationwide search. Most of the other logical successors to Greenberg were under a cloud because of Spitzer's probe, they said.

"Michael Cherkasky is a proven executive with an enormous breadth of experience. He brings a history of innovation and will . . . reassure the regulatory authorities of our commitment to operate at the highest legal and ethical standards," the Marsh directors said in a statement.

Cherkasky said in an interview that he has a tough road ahead. Marsh stock has lost nearly half its value since Spitzer filed his charges.

"This wasn't a blip. This is a serious crisis for us here at MMC, but we're a company that is enormously healthy and fundamentally sound," he said. "We'll come back."

Cherkasky's expertise is in white-collar crime and financial misdeeds. In Morgenthau's office, he prosecuted mobster John Gotti and helped investigate the Bank of Credit and Commerce International.

He also made an unsuccessful run for Westchester County district attorney in 1993, vowing afterward that he would never run for political office again.

Cherkasky has been involved with investigating financial wrongdoing several times since then, serving in 1995 as an adviser to a California grand jury probe of the alleged derivatives fraud that brought Orange County to near bankruptcy. In 1997 he was named to monitor the Teamsters' union election and investigate the finances of James P. Hoffa, who was a candidate for the union's presidency.

At Kroll, he ran a public company with $800 million in annual revenue, far smaller than Marsh's $11 billion. But, as he pointed out, both are service industry businesses where "clients demand excellence and integrity."

Spitzer, for his part, was complimentary Monday about what he thought his former boss could accomplish at Marsh. "Mike is committed to changing the dynamics at the root of this," he said. His appointment "is a significant step forward for the company."

Cherkasky said he doesn't think his long-standing friendship will win him or his company an easier time.

"Bob Morgenthau trained me and Eliot Spitzer do the right thing and not dwell on the personalities," he said. "Eliot's not going to make the restitution one cent less because it's Mike Cherkasky on the other side."