The snickering began as soon as the shock from the 1994 election wore off. The Republicans had won back the Senate, and Alfonse D'Amato would become chairman of the Senate committee looking into Whitewater. Al D'Amato? The name was synonymous with sleaze. Would anyone take an ethics investigation under his direction seriously?

Probably not--or at least not without the help D'Amato has received from a New Jersey prosecutor with an ethical record that is the reverse image of his own. In Michael Chertoff, the chief counsel to the Senate Whitewater Committee, D'Amato has found a man able to make his political fishing expedition look credible. While Kenneth Starr, the independent counsel, quietly pursues his work out of public view, the committee has been chewing up Clinton associates and spitting out incriminating press. If anyone could pull off a face-to-face showdown with the First Lady, Chertoff could. "You don't want to be cross-examined by Michael Chertoff," says a reporter who followed him while he was a federal prosecutor in New Jersey. "Before you know it you'll look down and you won't have any clothes on. He'll have [Hillary] admitting that basically she's the biggest criminal to ever come out of Arkansas."

Chertoff, who looks older than his 42 years, bears an uncanny resemblance to Montgomery Burns, the ruthless nuclear power plant owner on "The Simpsons": the gleaming bald head, the bulging eyes, the pointed nose. With his stern demeanor, driven manner and Jersey accent, Chertoff contrasts sharply with his Democratic counterpart, Richard Ben-Veniste, whose blow-dried coif and p.r. smile invoke lunch at Mezzaluna.

Chertoff cultivated his cross-examination skills as a prosecutor in New York and New Jersey, where he earned a reputation as a tough-minded ethics hawk. "In his old life, D'Amato is the kind of guy Mike Chertoff would have prosecuted," says a Democrat who has followed the hearings closely.

How then, to explain his current alliance? Some say Chertoff is overzealous in his ambition; others argue he wouldn't risk his triple-A reputation on something he believed to be a political hatchet job. And while most people who have worked with or against Chertoff speak of him in superlatives, they also seem a little nervous when his name is raised: "It's really all positive," says one New Jersey Republican. "I don't want him to call me. I'm being very positive ... make sure you write it that way."

The young Chertoff clerked for Justice William Brennan after Harvard Law School, and then worked at the tony law firm of Latham and Watkins in Washington before joining the feds. His break came in 1986. As a prosecutor in Manhattan, Chertoff was thrown a blockbuster case by his boss, Rudy Giuliani: the trial of heavies from three of New York's biggest mob families. "I was scared to death," Chertoff says of his assignment. "Nothing has ever been quite as daunting again."

His colleagues watched in awe as Chertoff became one with the case, inhaling details from mountains of evidence and hundreds of hours of wiretap recordings. "I try to learn everything that's humanly possible about the subjects I'm going to examine on," Chertoff says. The goal is "to know more about the subject than the witness." And he did. Genovese family consigliare Bobby Manna was counting on a voice identification expert to discredit Chertoff's incriminating recordings of his plots. But in records from a case twenty years prior, Chertoff had unearthed evidence that ruined the expert's credibility. Chertoff recalls the "Matlock" moment with relish. "I said, `Isn't it a fact that you couldn't even recognize your own mother's voice?' And he takes a long pause, and he just says `Yeah.' The jury was rolling their eyes." Even the mobsters Chertoff sent to prison seemed to grasp the status he'd won by nailing them. A 1992 New Jersey Law Journal article recounted an exchange between a police sergeant and racketeering convict "Fat Tony" Salerno, who inquired about his former tormentor:

Salerno: I was watching TV last night and I saw that fuckin' "Trade-Off" talking about something. He's out in Jersey now. Does he have some big job over there or something?

Officer: Yeah, he's the number-two guy over there, Tony. You know, like the consigliare. He's doing good. He's going to go a long way.

Salerno: Well, you give him a little message from Fat Tony. You tell that son of a bitch he owes me a thank-you note.

Out in Jersey, Chertoff was on his way to becoming the state's U.S. attorney. He took over a moribund office and boosted its profile--and his own--through a series of heavily publicized cases involving political corruption and white-collar financial crime, the twin pedestals of the Whitewater investigation. Chertoff, a registered Republican, distinguished himself enough to survive a 1993 Clinton purge of Republican appointees, thanks in part to help from Democratic Senator Bill Bradley. He returned in 1994 to Latham and Watkins, and shortly thereafter received the call from D'Amato, to whom Chertoff had been recommended by former fed colleagues from New York, admirers of his mob-busting success.

One longtime friend of Chertoff says that he "is philosophically grounded.... Michael has a very clear sense of what he perceives to be right and wrong." Maybe. But he'll have to tread carefully in the coming weeks to avoid overkill. He stumbled for the first time last week while pressing Webster Hubbell about legal work he undertook after resigning as associate attorney general. The moment provided a vision of how the tables could turn: Chertoff seemed to suggest that money may have tainted Hubbell's testimony. Suddenly Hubbell was the folksy good guy, Chertoff the bullying henchman. "That's pretty rotten," responded Hubbell, his lips quivering. D'Amato intervened to adjourn the hearing.

But it was Chertoff's first major gaffe; and he doesn't need to score an impeachment to exit the Whitewater saga a GOP hero. Will he emulate Giuliani, the man who gave him his break, and parlay crime-fighting into political office? There are whispers to that effect, but Chertoff downplays them. It's more likely that he's appointment-bound--to the federal bench or to a post in a future Republican Justice Department. Of course, if this thing against the Clintons really takes off ...

Just ask Fred Thompson, the former Watergate lawyer who now represents Tennessee in the Senate. Or the one who now lives in the White House.