By Paul Reynolds
BBC News Online world affairs correspondent
The 2004 American presidential election is shaping up to be a rough one by recent standards with questions already rife about President Bush's National Guard service and Senator John Kerry's private life.
Kerry dominates the Democrats
But in historical terms, this is quite mild stuff and there is a moderating influence these days in that the heavyweight US media are reluctant to get involved in what they see as private issues.
Both the New York Times and the Washington Post, for example, have written about whether President Bush actually carried out his duties as a pilot in the Texas Air National Guard in 1973.
That has public importance given that trust and national security issues are major campaign themes. John Kerry's record as Senator and the support he has or has not received from lobby groups are also obviously fair game.
But neither paper has covered the John Kerry story which engaged the attention of websites, radio and TV talk shows, some of the tabloid papers and elements of the foreign press.
The Kerry story
The story was about whether Senator Kerry had a recent affair with a young woman.
The question, it appears, was first raised by aides in the campaign of retired General Wesley Clark, who himself was quoted as saying that Kerry's campaign might "implode". It has not so far and Clark has even endorsed Kerry himself.
Senator Kerry himself said initially: "There is nothing to report" and then when that was challenged as a Clinton style non-denial, he stated clearly enough: "I just deny it categorically. It's untrue."
The young woman herself then issued a statement saying that there never had been a relationship. Her parents even said they would vote for Mr Kerry. End of story, really.
Mainstream media defence
The Washington Post London correspondent Glenn Frankel, a Pulitzer Prize winner and former editor of the Post's Sunday magazine, defended his newspaper's editorial judgment, which has proved correct.
"We've been down this road many, many times before. We are extremely reluctant to follow this kind of thing up unless there is a really, really compelling public interest. We don't feel there is any reason to until it reaches a threshold," he said.
Making accusations is a delicate game because it can all can backfire. Allegations, rumours even, are often often floated through the internet to see how far they get. In the Kerry case they have got nowhere. Both campaigns muster big teams to counter whatever might emerge.
A dirty trick which went wrong has already been exposed. This involved a photograph showing a youthful John Kerry sitting alongside Jane Fonda as she made a speech during an anti Vietnam war rally.
It turned out that two photos had been put together. In the original one of John Kerry, he is sitting on his own.
A long tradition
Dirty tricks, though, are part of American political life.
Indeed, it used to be far worse.
Richard Nixon was a master of the art in large ways and small. In 1968, when Nixon was running against Vice President Hubert Humphrey, the Republicans are believed to have persuaded the South Vietnamese to withdraw from a peace conference being organised by President Lyndon Johnson. The subsequent diplomat fiasco is felt to have damaged Humphrey's chances.
1968 appears to have a vintage dirty tricks year. Former Senator George Mitchell once remembered campaigning with Senator Edmund Muskie in the primary races: "We encountered what then seemed inexplicable, crazy events. Everywhere I went on the road, there would be a bill for $2000 in the restaurant and bar signed with my name. One day, 15 limousines showed up signed in my name. At four o'clock in the morning, 500 pizzas were delivered, ordered in my name."
Nixon carried on with his tricks on the 1972 campaign when the Democrats' headquarters in the Watergate building were broken into. The discovery did not stop him from winning the election that year but it did have somewhat serious consequences subsequently, showing that to be dirty is not necessarily to be smart.
Nixon in turn had always accused the Kennedy campaign of fixing elections in Illinois in 1960, thereby denying him victory.
Losing an election
There was one infamous dirty trick in the nineteenth century, told by Richard Shenkmann in his book Presidential Ambition, which might have cost one candidate the presidency.
The candidate was Democrat Grover Cleveland and two weeks before the election in 1888, he seemed to be in the lead.
Then the Republicans released a letter from the British ambassador to one Charles F Murchison, an Englishman living in California.
The letter supported Cleveland's candidature and naturally this upset Irish Americans voters in New York who promptly deserted the Democrat.
He lost the election.
It turned out that "Charles F Murchison" was no Englishman but George Osgoodby, a Republican who had managed to get the ambassador's opinion by stealth.
The election of 1828
One of the most vitriolic elections was in 1828.
John Quincy Adams was nicknamed "The Pimp" by the campaign of his opponent General Andrew Jackson, based on a rumour that he had once coerced a young woman into an affair with a Russian nobleman when he had been American ambassador to Russia.
Adams' supporters hit back with a pamphlet which claimed: "General Jackson's mother was a common prostitute brought to this country by British solders! She afterwards married a mulatto man with whom she had several children of which number General Jackson is one!!" Jackson won anyway.
And just to show that this kind of thing goes right back to the start of American campaigning, we have the election of 1800 in which Thomas Jefferson was accused of favouring the teaching of "murder, robbery, rape, adultery and incest". Jefferson won. He did not teach the offending subjects.
George Bush and John Kerry have got off quite lightly.