The anonymous e-mails and letters began dropping into inboxes and through front doors this summer.

One claimed that Hillary Clinton was having a lesbian affair with Huma Abedin, her beautiful aide. Another online mass-mailing cautioned of the “dark secrets” of Mitt Romney’s Mormonism. A blogger claiming to support John McCain said that Rudy Giuliani's wife supported the killing of “innocent puppies”. Flyers appeared on cars accusing Barack Obama of being a Muslim extremist. An anonymous website said that Fred Thompson was a corrupt playboy.

Welcome to South Carolina, the foulest swamp of electoral dirty tricks in America. This state’s primary race has already become the sleaziest leg of the 2008 presidential campaign.

Here, political operatives know only one way to win: take your opponent’s head off. The Palmetto State’s primary follows hard on the heels of Iowa and New Hampshire and is the candidates’ first foray into the Deep South. For Republicans, in particular, it is crucial: since South Carolina gained its first-in-the-South status in 1980, no Republican has received the party nomination without winning the state.

“South Carolina is a do-or-die state again,” said Rod Shealy, a veteran Republican consultant, over a meal of fried pork and beans in his favourite diner, the Lizard’s Thicket. “The attacks are already coming on a daily basis. And with the anonymity of the internet, we’re going to see new lows in dirty politics that would have been unimaginable recently.”

Mr Shealy knows a thing or two about dirty politics. In 1990, when running his sister’s campaign for lieutenant governor, he paid an unemployed black fisherman facing felony charges to run for Congress to increase white voter turnout. He was convicted of breaking campaign laws.

Mr Shealy is among a small band of political consultants who wield enormous influence in South Carolina. They are bitter rivals and all learnt their trade from Lee Atwater, a South Carolina native and the first President Bush’s notorious and venal attack dog. Dirty politics ran in his blood. He once explained that the way to win a campaign lay in “strippin’ the bark off an opponent”.

The most grizzled political veterans until recently believed that the apogee of their state’s slash-and-burn mentality was reached in 2000, when John McCain’s presidential ambitions were emasculated by operatives working for Mr Bush.

After losing badly to Mr McCain in New Hampshire, the Bush team knew – as one operative says – that they had to “chop him up” in South Carolina. Flyers appeared saying that Mr McCain had fathered an illegitimate child with a black woman (he and his wife have an adopted Bangladeshi girl). A whispering campaign was started claiming that his five years as a Vietnamese prisoner of war had made him mentally unstable. His wife was a drug addict, people were told in anonymous telephone calls. Mr Bush and his former chief strategist, Karl Rove – another Atwater protégé – always denied any involvement. But Mr McCain’s campaign never recovered.

The brutality of South Carolina’s Republican primaries has until now involved the state’s hatchet men putting the party’s establishment candidate – Mr Bush in 2000 – back on track after upsets in Iowa or New Hampshire. What is different this year is that at least four Republican candidates – Mr McCain, Mr Romney, Mr Giuliani and Mr Thompson – are all heading to South Carolina with a realistic chance of winning the state. That means that the traditional two-man showdown will be replaced by a multi-candidate massacre among a group of men ripe for attack.

“The question this year is not whether the race will be dirtier than 2000,” said Will Folks, the former spokesman for Mark Sanford, the Republican Governor of the state. “The question is, when will it cross that threshold?”

The man who masterminded the destruction of Mr McCain in 2000 is Warren Tompkins, known by some operatives in South Carolina as the “God of Hell”. He has been hired this year by Mr Romney. He has already had to answer questions about his tactics.

The anonymous anti-Fred Thompson website PhoneyFred.org was traced to his consulting company.

He claimed that it was the act of an errant employee acting independently. Mr McCain has hired Richard Quinn, another of the state’s top consultants. Mr Folks says that the Tompkins and Quinn camps are using two websites, The Shot and The Palmetto Scoop respectively, which masquerade as objective blogs but in reality peddle daily dirt on opponents.

“ A picture of Mr Giuliani wearing drag at an event when he was New York’s mayor has appeared frequently. The day after scurrilous anonymous phone calls were made to New Hampshire voters about Mr Romney’s Mormonism this week, The Palmetto Scoop claimed that it was a ruse by the Romney campaign “to drum up sympathy for the candidate.” Mr Romney will need all of Mr Tompkins’s hardknuckle guile in a state where many social conservatives view Mormonism as a cult. The night before a Republican debate in May several conservative activists received an anonymous, eight-page letter entitled Mormons in Contemporary American Society: A Politically Dangerous Religion?

Nobody is sure who is behind the attacks on Mrs Clinton and Mr Obama, but the claims of lesbianism and Islamic extremism have found fertile ground on right-wing websites. Mr Obama, a Christian, was forced to deny the rumours at a campaign event on November 9.

Lee Bandy, who has written about South Carolina politics for 40 years, says of the Republican campaign: “The race is so close this year there is no telling what these guys will do to win. And a guy like Rudy Giuliani is a prime target.”

Times Recommends

• 'New York has lost its edge'
• Copenhagen will fail – and quite right too
• More than 17,000 new underwater species found