FOR 12 years, Deborah Jeane Palfrey kept a record of every phone number dialled by her business. She claims that Pamela Martin & Associates was a "high-end adult fantasy firm which offered legal sexual and erotic services" to wealthy Washington DC patrons. This week, having secured the permission of the judge in her trial for running a £150-an-hour brothel, her lawyers released those phone lists to anyone who wanted them. It has been a nervous few days for the capital's most libidinous politicians.

"Once more analysis is done, more names will come out," promised her lawyer, Montgomery Blair Sibley.

The "DC Madam" scandal has been a staple of congressional gossip for months but on Monday it claimed its first senator. David Vitter is an old-fashioned, God-fearing, family-values conservative from Louisiana who has built his platform on opposition to abortion in any circumstances, including cases of rape and incest.

Tipped off that Hustler magazine was about to link him to the alleged prostitution ring, Vitter released a classic sackcloth and ashes statement: "This was a very serious sin in my past for which I am, of course, completely responsible," it began.

"Several years ago, I asked for and received forgiveness from God and my wife in confession and marriage counselling. Out of respect for my family, I will keep my discussion of the matter there - with God and them. But I certainly offer my deep and sincere apologies to all I have disappointed and let down in any way."

Shortly after this show of penitence, Hustler publisher Larry Flynt claimed the scalp for himself, in a press release which boasted that "within hours of obtaining the phone records, Flynt's team found what ABC News has so far been unable to ferret out".

ABC will be ruing a missed opportunity. The network's star investigative reporter, Brian Ross, was handed the last four years of Palfrey's phone records in March but decided the high-ranking army officers, federal investigators and World Bank officials he found "weren't newsworthy enough" to name.

Randall Tobias, a deputy secretary of state, resigned the day after being confronted, before Ross could out him.

The revelation that Tobias was an escort service regular set the tone for a story that the Republican Party, in particular, is finding difficult to shake. It is not about the act of paying for sex, but the stunning hypocrisy of the men who were doing so.

In his role as the head of the Bush administration's Agency for International Development, Tobias was responsible for allocating overseas aid, including payments to organisations attempting to stop the spread of the HIV virus. Under his direction, the agency withheld money from NGOs until they introduced strict anti-prostitution policies. He promoted the ABC approach to sexual health: A for Abstinence, B for Be faithful to your partner and C for Condoms as a last resort.

"This was a guy leading a crackdown on prostitution worldwide," Ross said. "The fact that he was a repeat customer of this and other services, the hypocrisy made that important."

This has been the abiding principle of Larry Flynt's campaign, which began in June with a full-page advert in the Washington Post, offering up to $1 million for "documented evidence of illicit sexual or intimate relations with a congressperson, senator or other prominent officeholder".

The pornographer is making no claim to the moral high ground when it comes to sex but, as he observed at a press conference on Wednesday: "When someone is living a lie contrary to the way they are advocating in their public lives, they become fair game."

Vitter, he continued, "is to the right of Attila the Hun every step of the way. Unfortunately, there are too many of these guys in Congress, and I am going to do my part in getting them out of there. I don't want a man like that legislating for me, especially in areas of morality. This is payback time."

Vitter is particularly vulnerable to the charge of hypocrisy because the sanctity of marriage is such a fundamental component of his political agenda. "Marriage is a core institution of societies throughout the world and throughout history," he said recently.

"It's something that has provided permanence and stability for our very social structure."

Vitter co-authored a proposed amendment to the constitution that would have made civil unions illegal nationwide. When he was asked to list his primary concerns after Hurricane Katrina had levelled huge swathes of his Louisiana constituency, he replied without hesitation that gay marriage was the greatest threat facing America.

He was also one of Bill Clinton's most outspoken critics during the Monica Lewinsky affair, arguing that if Congress failed to impeach the president on moral grounds, "his leadership will only further drain any sense of values left to our political culture".

Vitter can be thankful that relatively few of his supporters have reached the same conclusions about his own fitness to govern. Vincent Bruno, of Kenner, a former New Orleans police chief, said the senator should resign "for his own good, the good of the party and the good of his family", but generally Louisiana's Republicans are prepared to forgive, and inclined to forget his indiscretions as quickly as possible.

"I'm very disappointed, but I think this is a family matter and I'm praying for him," said state representative Kay Katz, adding: "I support things that Senator Vitter has advocated and will continue to support those things."

The Reverend Mark Foster told his local paper, the News Star, that "if God has forgiven him so surely can I."

The Reverend Billy McCormack, leader of the Louisiana Christian Coalition, concluded that "Senator Vitter may well be much more able as a senator now than before because people tend to learn from their mistakes when they are responsible. I will continue to support him fervently."

Vitter has been in hiding all week, holed up with his family as new claims emerged that he paid weekly visits to prostitutes in New Orleans over a period of several years.

Jeanette Maier told Associated Press that in the mid-1990s Vitter was a regular at the Canal Street brothel she ran with her mother and her daughter.

"I'm not out to ruin a marriage," she said. "I want his wife to see what a wonderful man he is.

"He is a decent guy. He's not a freak. He's not using drugs. I know he's not a person that would down-talk a woman. I know that he's respectful. I want his kids to know he's a good father. Just because he had sex out of wedlock - so what? At least he stayed with his kids."

Larry Flynt claims to be in contact with five women who will testify that they had sex with the senator for a share of Hustler's $1 million reward but, even if they can all prove the truth of the allegation, it might not be enough to derail Vitter's political career.

Three key factors count in his favour. First, he is not up for re-election until 2010, and three years is a long time in politics. Second, the Democrats don't have a credible challenger in Louisiana. Third, the state has such an inglorious history of corruption and sleaze that voters have come to expect, and tolerate, bad behaviour from congressmen.

Vitter was elected to the House Of Representatives in 1999, after an adultery scandal led to the resignation of his predecessor, Bob Livingston. In the mid-term elections of 2006, Democrat William Jefferson won re-election to Congress, six months after FBI officers allegedly taped him soliciting a bribe and found $90,000 of cash hidden in his freezer.

Edwin Edwards, the only man to serve four terms as Louisiana governor, was dogged by accusations of corruption throughout his time in office. He was caught paying gambling debts with suitcases full of money and stood trial for mail fraud, obstruction of justice and bribery. He once boasted that the only way he could lose an election was to be "caught in bed with a dead girl or a live boy". In 1991, he was elected for the final time, after supporters produced a bumper sticker reading "Vote For The Crook. It's Important." He is currently serving 10 years for fraud and extortion.

Even if he does survive in the Senate, Vitter still has reason to worry. Seven years ago, when his wife Wendy was asked by the Times-Picayune newspaper if she could forgive infidelity should her husband stray, she replied: "I'm a lot more like Lorena Bobbitt than Hillary Clinton. If he does something like that, I'm walking away with one thing, and it's not alimony, trust me." For now, she is standing by her man.

Vitter's fall is a blow to Rudy Giuliani's presidential bid, because he is the former New York Mayor's southern campaign chairman. Giuliani has been married three times, twice too many for the Republican base, and he can ill-afford to lose more heartland votes. The wider political significance of the scandal depends on who else appears on the phone records of Pamela Martin & Associates.

Ever since they were released, teams of volunteers from anti-George Bush activist group Citizens For Legitimate Government have been calling every number on the list and posting the results online.

Spokeswoman Lori Price said: "I believe it will make a difference politically because of the pattern, the cumulative effect of so many people that are espousing conservatism and family values being caught lying.

"A crime is a crime, but it's so much more egregious if you're preaching against it beforehand. There's a burgeoning anger in the United States at the hypocrisy and double-standards of this government. The Libby pardon is part of the same illness. The Foley page scandal is part of the same illness."

In September 2006, Republican congressman Mark Foley, a prominent campaigner against child pornography, resigned after sexually explicit messages that he sent to a teenage office assistant were made public. In November, leading evangelical pastor Ted Haggard admitted to being "a deceiver and a liar" after a gay prostitute revealed that Haggard had paid him for sex and crystal methamphetamine.

There is a clear parallel to be drawn with John Major's ill-fated "back to basics" initiative. The indiscretions of David Mellor, Tim Yeo, Neil Hamilton, and Jonathan Aitken contributed to a pervasive sense that Major's government could not be trusted, thus creating the conditions for Tony Blair's sweeping election victory in 1997.

With Larry Flynt playing the role of Max Clifford, the Democrats will be hoping for further scandals before the United States goes to the polls next year.