Jan. 16, 2008  -- The Swift Boat Veterans ads in 2004 attacking John Kerry's exploits in Vietnam, the infamous Willie Horton ad in 1988 that portrayed Mike Dukakis as soft on crime, and the notorious 1992 "Read my lips" spot that focused on the then-President George Bush breaking his earlier pledge to not raise taxes.

All three ads may be derided by the pundits as negative advertising, but there is little doubt that they worked: They helped turn the elections against the targeted candidates.

The ads were products of opposition research, nuggets of damaging information about political candidates uprooted by their opponents to damage their reputation or credibility in the eyes of the voters.

And one of their prime manipulators has finally stepped out from the shadows to reveal his tactics and role in tipping numerous elections around the country over the last decade and a half.

Stephen Marks, an opposition research specialist for more than 12 years, worked on some of the most competitive bare-knuckles elections in recent years, including the 1996, 2000 and 2004 presidential elections, the second North Carolina Senate race between Jesse Helms and Harvey Gantt in 1996, and the Georgia Senate race between Max Cleland and Guy Millner.

He also dug up dirt for scandal-plagued lobbyist Jack Abramoff and his partner Mike Scanlon, oil company Koch Industries, and he helped former House Majority Leader Tom DeLay look up negative info on his nemesis, Texas prosecutor Ronnie Earle, who was targeting DeLay for campaign finance violations.

Marks, who recently retired from his career in opposition research, tells all in his new book, "Confessions of a Political Hitman: My Secret Life of Scandal, Corruption, Hypocrisy and Dirty Attacks That Decide Who Gets Elected (And Who Doesn't)."

Although he doesn't literally murder people, Marks writes that "I assassinate them with their own words and deeds, digging dirt wherever I can find it." And that dirt includes politicians' own records as public officials and professionals, their financial records and their personal lives.

Marks makes no apologies for his career. "Whether negative stuff is good or bad, people have a right to know," Marks tells ABCNEWS.com. "You have to back up your info with facts, unlike positive ads that tend to focus on promises. The researchers give the candidates the straight facts, and if they want to take those facts and skew them and take them out of context, that's on them."

After years of realizing after an election that he'd actually been working for "the bad guy" against "the good guy," Marks grew disillusioned with the Republican Party and what he calls its hypocrisy on "family values" issues.

"A lot of me was going in idealistic, as a true believer, only to find out that a lot of these guys, once they get the trappings of power, it's very hard for them to give that up," he explains. "The Republicans were no different form the Democrats when they were in full control, and I thought they wouldn't make the same mistakes or have the same arrogance."

Among his proudest accomplishments was his creation of an anti-Gore ad in 2000 that showed Gore defending the Rev. Al Sharpton followed by footage of Sharpton telling college students to "off the pigs" (or kill cops) and Sharpton calling America's Founding Fathers the "scum of Europe."

Marks believes that ad, which was paid for by an independent group, helped swing Florida to Bush. "That ad received so much attention and got a lot of TV airplay," he says. "I hope that maybe it did move that many votes in Florida."

Marks also resurrected the infamous Willie Horton ad when he was working for then-Massachusetts Gov. William Weld in his 1998 race for John Kerry's Senate seat. Back in 1992, Kerry, as a private attorney, had secured the early parole of a career criminal, George Reissfelder, who had pleaded guilty to the attempted murder of a police officer in Florida. After he was paroled, Reissfelder got involved with a Mafia-controlled drug ring in Boston and was questioned by the police regarding the Gardner Museum heist, the biggest museum robbery in U.S. history.

Marks' ad featured Reissfelder's picture morphing into a photo of Willie Horton.

But the episode ended up starting to prick at Marks' conscience -- he received death threats from Reissfelder's relatives. And he got a phone call from Reissfelder's niece, telling him that she never knew about her uncle's history of crime. "Unfortunately, good people are sometimes related to people who do bad things and these good people sometimes get hurt in the process."

Back in 2001, Marks worked for Jack Abramoff's partner, Michael Scanlon. Among his tasks was to fly to the New Orleans airport, pick up a Fed Ex package full of hundreds of envelopes and mail them from the airport post office. Marks took a peek into one of the envelopes and found that they contained fliers promoting a preferred candidate, "Poncho," for the presidency of an Indian tribe, Louisiana's Couchatta tribe.

The tribe was one of the scandal-tarred lobbyist's clients, and Marks figured that by interfering in the tribal election and getting their man in control of millions of dollars in casino profits, Abramoff and Scanlon would reap plenty of money in lobbying fees.

Another of Marks' tasks for Scanlon involved researching Gus Boulis, the owner of SunCruz, a casino boat chain in Florida, who had backed out of a deal to sell his business to the lobbyist duo. Marks' assignment was interrupted when he was awakened in the middle of the night and told by his client to "Get the hell out of Dodge." Earlier that day, Boulis had been gunned down -- killed by mobsters. Because his name appeared on countless requests to research court documents involving Boulis, Marks ended up being questioned by Fort Lauderdale police.

Now, Marks realized that "I was merely a pawn helping bad guys break the law."

Marks relishes telling stories about his wild romantic life as a borderline sex addict; on a routine trip to the Texas state comptroller's office to do research in 2002, he had sex with a young assistant in the meeting room. "Despite knowing intellectually that using women sexually was morally wrong, I couldn't control myself."

Maybe it was a case of bad karma, but Marks ended getting a taste of his own bitter medicine when one of his numerous lovers went psychotic, obtaining his cell phone records and calling every number on the list, telling everyone that Marks was an ax murderer, pedophile and other "outrageous accusations."

One of his friends had to get police protection after the ex-lover showed up unannounced and Marks ended up filing an FBI report to stop the harassment.

Some of Marks' tactics were even considered too dirty for some of the candidates he was helping.

During the Bush-Clinton election in 1992, Marks uncovered photos of Bill Clinton sharing a podium with "Q Bone" and Leon Gulette, two former gang members, at an event to promote a truce between the Bloods and the Crips. Marks believed that photos of the event, at which Clinton told "Q Bone," a convicted killer, "I need your help" was a smoking gun that would have damaged the candidate.

Marks even faxed copies of the photo and its caption to Bush's top campaign advisers. But they never used the issue against Clinton, which Marks attributes to a fear of being labeled racist.

When Marks helped unearth information about former House Minority Leader Richard Gephardt's real estate deals that appeared to violate IRS and federal banking laws, he was shocked that it took over a year for any Congress member to file a complaint against Gephardt with the House Ethics Committee, which eventually dismissed allegations against him.

"I gave the Republicans the goods, and they apparently were either too cowardly or too frightened by the thought of their own unethical behavior coming to light to take any action against Mr. Gephardt."

During the Cleland-Millner election, Marks was so desperate to get a photo of Cleland posing with Ted Kennedy's nephew, Michael, at a veterans center that he lied to one of the vets, claiming that his uncle was in the picture so that Marks would be permitted to get a copy of the photo.

The most effective opposition research focuses on revelations that are clear and simple for the public to understand, says Marks.

When George H.W. Bush was trailing Dukakis at the polls, his staff brought in file cabinets full of anti-Dukakis research to legendary campaign manager Lee Atwater. But Atwater told them to get rid of the file cabinets and bring him one index card with three simple hits to be used against Dukakis: Willie Horton (while on furlough, the convicted murderer raped a woman and pistol-whipped his fiancée), the Pledge of Allegiance (as governor, Dukakis opposed public school children reciting the pledge), Boston Harbor (Dukakis claimed that he had "cleaned up" the harbor, which was notoriously dirty).

Not all his exploits were political. Marks was also hired by Charles and David Koch, heirs to an oil fortune, during a nasty feud with their brother Bill. But the gambit backfired because Marks realized that there was more negative information out there about his own clients, including evidence of environmental damage caused by the brothers' oil company.

"So not only does Oppo Man help elect low-life politicians too incompetent to discuss with a straight face, he also helps guys like Jack Abramoff and companies like Koch Industries, just because they are connected to the Republican Party?" Marks writes.

Several of his clients had more skeletons in the closet than their opponents, and no amount of opposition research could repair the damage.

While working for Democrat Shane Guidry, who was trying to unseat Louisiana councilman Butch Ward, it was revealed that Guidry's father had pleaded guilty to paying former Gov. Edwin Edwards $1.4 million in bribes to get a casino license. Guidry was trounced in the election and was later arrested and charged with battery after getting into a shouting match with Popeye's Famous Fried Chicken founder Al Copeland during a brawl at a steakhouse.

Another of his clients was Don Goldwater, the nephew of Republican legend Barry Goldwater, who wanted to run for governor of Arizona. Marks uncovered that Goldwater held some incendiary beliefs, including that all illegal immigrants are criminals who should be forced into labor camps.

In an ironic twist tailor made for an opponent's campaign ads, Goldwater's father had been busted for repeatedly hiring illegal aliens and allegedly forcing them to live in unlivable conditions. Goldwater ended up stiffing Marks until the researcher threatened to leak the damaging info to the press -- he was paid the next day. Goldwater did not return calls for comment.

Marks became disillusioned by the GOP during the impeachment debacle in which he blames Republicans for dropping the ball due to their own indiscretions and ethical quandaries.

Among the Republicans he blames: current presidential candidate Fred Thompson. David Schippers, the counsel for the House Judiciary Committee during the Clinton impeachment saga, believed the most egregious alleged offenses by Clinton had nothing to do with Monica Lewinsky but rather the illegal Chinese campaign contributions allegedly made in exchange for military secrets.

But when Schippers reached out for more information from then-Sen. Thompson, who was heading the Senate investigation into the matter, he was told, "Stop, it's over."

"Thompson flunked the test," writes Marks. "From the beginning, he went straight into the tank." Marks blames Thompson for arguing that the Independent Counsel statute should not be allowed to exist and for claiming the investigation should be headed by Clinton appointee Janet Reno.

A spokesman for the Thompson campaign responded, "Just like he did during his work in the Watergate hearings, Sen. Thompson believes the role of the hearings was to determine the truth regardless of political party. However, the senate committee was given neither the tools nor the time to be successful in the investigation."

In the current presidential campaign, Marks says that none of the negative ads seem to have worked.

"Both Obama and Huckabee won in Iowa, despite negative ads against them," he says. "So far in New Hampshire, McCain won purely positive. But it's early in the campaign. I can assure you that there will be plenty of negative stuff still to come."

He insists that negative campaigning and opposition research are a "necessary evil which will be needed if the electorate is to cast educated and intelligent votes." And that any candidate who doesn't research himself and his opponent is a fool who deserves to lose, he says.