Ed Becker is the political trouble business. From his home town of Las Vegas, 57-year-old Becker prowls the country working for -- or against -- politicans, digging for dirt, pursuing an art politely termed "opposition research." And sometimes he works the other side of the street, tracking dirtmongers spreading negative information about his client.

In a time when a politician's best currency is a squeaky-clean reputation, professional dirtmongers are about as welcome as double-digit inflation. But like the flight crew of the Enola Gay, they exist because someone has to do the job.

For $35-an-hour and expenses, Becker often works at the behest of a Washington attorney with close ties to the Republican Party, a lawyer whose identity he perfers not to reveal.Among the tools of Becker's trade are "a guy who can go in any bank account," a voracious appetite for reading, and a photographic memory for details and conversations.

"I can be anybody," says Becker, who, driving through Vegas traffic, looks as anonumous as any midwestern savings and loan burgher in town for a convention. "An undercover guy is really a frustrated actor. He's like the guy arrested 15 times for being a doctor, priest or scientist -- except he's legal."

When Becker introduces himself as a writer (which he sometimes is) or an oil businessman (which he says he once was) he may not be breaking any laws, but politicians still don't much like to talk about the Ed Beckers of the world. Especially Republicians, for whom Becker usually works.

The problem: Political sleuthing got a bad name when the Watergate caper revealed a Howard Hunt-interviewing ex-ITT lobbyist Dita Beard in an ill-fitting wig, an Anthony Ulasewicz prowling around Chappaquiddick, a James McCord sniffing for scandal at the Democratic National Committee headquarters.

"Since Watergate," says Becker, "Republicans aren't going to roll over any more and be accused of doing all the nickel-and-dime stuff they were accused of, though I agree it happened. Still if you went to Ronald Reagan and said, 'I'm an undercover guy, and I'm going to dig up dirt on your opponent,' he'd turn green and throw you out.

"But any of their upcoming guys -- they want to investigate every rumor, every business practice before they pick this guy to become the next governor, senator or president. When you tell a guy, 'Hey, pal, we just found out you were doing business with a guy in Kansas City, so forget it -- be a supporter, not a candidate,' well I think that's a smart move," says Becker, who stresses that he works on a free-lance basis for individuals -- not the Republican Party.

Though post-Watergate morality still reigns and political tricks are supposed to be a bad memory from the Nixon ear, opposition research is as much a part of politics as bumper stickers and balloons. And it's a safe bet that both the Ronald Reagan and Jimmy Carter camps are stocking their arsenals with negative information in preparation for autumn duels.

When George Bush enjoyed a fast takeoff after winning the Iowa Republican caucus, his backers noted as proof that Bush was a serious comer the fact that people were suddenly searching for scandal in his past.

It didn't help Bush in later primaries, but the results of the searches were meager. Ronald Reagan's New Hampshire campaign staffers reportedly turned up only one anti-Bush nugget: In a book about the 1976 presidental campaign, journalist Jules Witcover wrote, "Everyone knowledgeable in Republican politics considered Bush incompetent to be president." That quote was happily pointed out to political reporters.

When a newspaper resurrected a two-year-old story about Bush receiving a $106,000 donation for his 1970 Senate race from a secret Republican campaign fund, Bush placed a phone call to a friend in Washington who put Bush together on the phone with Ed Becker. "They were starting to ask him about Watergate up there in Maine," Becker quotes Bush as saying.

Becker had done some sleuthing for the Republicans when the Watergate scandal began to develop in the '70s -- "not to whitewash the thing as much as to see what the hell was happening," he says today -- and so he was able to remind Bush of the details of the hidden campaign fund. That permitted Bush to answer reporters' questions with enough specificity to help defuse suspicion that he's been involved in any funny money games.

Both the Republicans and Democrats regularly employ staffs to cull newspapers for potentially embarrassing quotes by opponents. Special-interest groups hire staffers to compile reports on candidates who support or oppose them. Researchers look for private bills a politician might have introduced in Congress, junkets, military academy appointments, board of directorships, and memberships in social organizations that might discriminate in choosing new members.

"First we did a matrix of a candidate's staff," recalls a former Democratic campaign adviser. "Any relatives on his payroll back home? We'd compare that with what the congressman indicated in his staff directory.

"Then we'd pore over his votes on bills and run the findings against his stock holdings, looking for a conflict of interest. If he was a lawyer, we'd check him out -- see who his clients are and cross-check that with his voting records. Of course, we'd go over a list of his contributors."

Not everyone jumps at the chance to become a dirtmonger. In the last two weeks, for example, a Washington free-lance writer named Edward Roeder who specializes in writing about campaign financing says he received three calls from congressional candidates. They wanted to know whether, for a fee, Roeder would look for questionable campaign contributions their opponents might have received. The reporter declined.

It isn't a pretty way to make a living. The dirtmonger labors alone among fluorescent lights and dusty files. To discover a congressman's assets, liabilities and income from outside sources means sitting in small rooms on Capitol Hill, poring over personal financial statements which the law requires be available to the public. Congressional committees keep records of junkets -- that means more rooms, more numbers.

Records of campaign donations are filed at the Federal Election Commission on K Street. To spend hours looking at names and numbers -- receipts for chicken-dinner fund-raisers are mixed in with mentions of individual fat-cat givers -- isn't a party.

And reaching people such as accountants and business associates who might be able to say unflattering things about a candidate is no cakewalk. Phone messages go unanswered, doors close in your face and suddenly everyone is in a meeting. The hunt doesn't often pay off -- but there's always the chance, and there's always simple luck.

Sometimes a politician's past returns to haunt him by chance. In the case of Sen. Thomas Eagleton (D-Mo.), it was a tipster's calls to a midwestern newspaper in 1972 that led to the story of his electroshock therapy and the early damage to the presidential campaign of George McGovern.

In another case, a New York-based investigator, A. J. Woolston-Smith picked up a rumor in March of 1972 that some anit-Castro Cubans were working to bug the Democratic headquarters in Washington. He alerted the DNC three months before the break-in was discovered. Historians can only guess how different the world might have been had the Democrats paid more attention to that early warning and the Nixon administration survived the scandal.

Then there's the defector from the opposing camp. In February a worker in the campaign of Clark Gruening, a challenger to Alaska's Sen. Mike Gravel in an upcoming Democratic primary, switched to the Gravel team. He told Gravel that Gruening's associates had been snooping around a piece of Aspen real estate Gravel owns with some partners. He charged that the Gruening camp had fed damaging information about the real estate deal to The Anchorage Daily News, a charge Gruening's campaign staff denied. Then the Gravel team filmed a quick television commercial starring the defector. It's a tough game.

Ed Becker, a round-faced pleasant-mannered man, began walking some of the nation's mean streets in 1955 when he became public relations director of the Riviera Hotel in Las Vegas. His milieu was gambling and men whose occupatons were vague. He helped piece together an NBC "White Paper" on organized crime in 1966 and later helped research the Vegas expose "Green Felt Jungle."

Last year his name surfaced publicly in connecton with the section of the House Assassination Committee report that alleged organized crime figures might have played a role in the killing of John Kennedy.

Becker told a House investigator that he made a new friend in September of 1962 while working undercover in Louisiana for a finance company investigating Billie Sol Estes. The friend was Carl Roppolo, a Shreveport oil geologist acquainted with organized crime mogul Carlos Marcello. Becker and Roppolo, says Becker, visited Marcello one night at his estate near New Orleans.And in the course of a long evening of drinking Scotch, Becker recalls Marcello cursed the Kennedy brothers and talked vaquely of trying to kill the president.

Marcello denied that, but the House report fingered Marcello as one of the two "most likely family bosses" to have participated in any assassination plot. t

For Becker, it's a kind of life -- shadows, suspicions and surmises.

Political sleuthing is no man's fulltime occupation, but Becker does more of the backdoor kind of investigating than, say, a young newspaper researcher at either of the national parties' headquarters.

For example, last fall Becker traveled to Miami and Kentucky and prowled around his home town of Vegas looking for derogatory information about John Y. Brown, then the Democratic candidate for Kentucky governor. aBecker talked to businessmen who'd had dealings with millionaire Brown in Florida and Nevada. If anyone has something scandalous to say about Brown, Becker was all ears. He turned up no evidence of wrongdoing by Brown, who won the election.

Then there's the other side of the street, protecting your man from other dirtmongers. Currently Becker is working for a client on the defensive. He's a prominent republican in state government (with higher ambitions) who has been linked vaguely in press reports to organized crime figures. Becker is working to find the source of the charges as well as to determine their validity.

Who pays for Becker's time and travel?

"Persons who prefer to remain unnamed," he says, though it is clear that he is paid by Republicans interested in the future of the GOP. In the case of his work against Kentucky's John Y. Brown, Becker says he doubts that Brown's Republican opponent knew of his efforts. "Understand there was no hanky-panky," Becker hastens to add. "I was really researching all of the political ties and associates of Brown, not sabotaging anything."

Discretion has always been of the essence in the dirtmongering business, and the neat, clean cases are the ones the public never learns about. Some snoopers, however, have not always done their work to great applause.

Six years ago Maryland politician Lawrence Hogan challenged Marvin Mandel for the governorship. An old friend, a former FBI agent knows an John "Fat Jack" Buckley, decided to help Hogan by rooting out Democratic corruption. But when word of Buckley's snooping got around Annapolis, bumper stickers appeared that read "Fat Jack Is Watching," and a flustered Hogan called off his hunt for dirt.

One of the more bizarre cases of Washington political snooping involved a young staffer at the Republican National Committee named Rita Carpenter and Rep. John Jenrette, a South Carolina Democrat involved in a highly publicized divorce.

In 1975 Carpenter worked as opposition research director for the RNC. She claimed that one assignment she received was to find juicy material on a Democratic senatorial candidate in New England by posing as a curious reporter, a charge the RNC later denied when she mentioned it to the press. But Carpenter earned the real enmity of her employer shortly after she began dating Democrat Jenrette.

Carpenter told People magazine, she had learned that the RNC was shadowing her dates with the congressman. Her bosses insisted it was not so, but Carpenter quit to report her charges on a network talk show, among other places.

Today Jenrette, under investigation for allegedly accepting money in the FBI's Abscam operation, is participting in an alcoholic rehabilitation program in Bethesda's National Naval Medical Center. Campaigning for him back home in South Carolina is his wife, the former Rita Carpenter.