WASHINGTON - Both John McCain and Barack Obama are promising a high-minded White House campaign.

WASHINGTON - Both John McCain and Barack Obama are promising a high-minded White House campaign.

But the dirt is already being dished up and could be spread by the bucket load soon.

"It's going to be Swift Boat times five - on both sides," one unidentified McCain insider was widely quoted as saying, anticipating a November match-up with Obama when and if Hillary Clinton bows out of the race.

The 2004 presidential election between George W Bush and John Kerry set a new standard for campaign mudslinging when the Democrat's Vietnam War record was impugned by a right-wing group called Swift Boat Veterans for Truth.

Before that, during his unsuccessful primary campaign against Bush in 2000, McCain was rumoured to have fathered an illegitimate black child.

The child, in fact, was a Bangladeshi orphan adopted by the Republican senator and his wife Cindy.

But enough of the mud clung to smother McCain's hopes in South Carolina and allowed Bush back into the year's primary race.

This time, the presumed Republican nominee has a "rapid response squad" to nip scurrilous rumours in the bud.

Obama has a similar operation, but has been powerless to prevent the spread of e-mails portraying him as a secret Muslim.

Those false rumours have continued to do the Internet rounds even as Obama battled to fend off incendiary sermons by his former Christian pastor, Jeremiah Wright, which look certain to come back in the form of attack advertisements.

Those adverts will not necessarily come from official Republican quarters but from shadowy "527" groups of the Swift Boat variety, named after the section of the US tax code that governs their political activity.

The Democrat could also be tarred by his links in Chicago to William Ayres, an ex-member of the anti-Vietnam War group Weather Underground, which bombed government premises from the late 1960s.

Obama's patriotism, and that of his wife Michelle, meanwhile has been the subject of vitriol on the powerful conservative talk radio circuit for months and already featured in attack adverts by the Tennessee Republican Party.

McCain may eschew the low road of campaigning, but Obama has already accused him of one "smear" for remarking that the Democrat is the favoured candidate of the Palestinian extremist group Hamas.

That suggestion prompted Obama to accuse McCain of "losing his bearings" - which the Republican's campaign took to be a veiled reference to his age.

At 72 next January, McCain would be the oldest president elected to a first term.

The age question is likely fodder for anti-McCain adverts, along with his entanglement in a 1980s corruption scandal as a member of the so-called Keating Five group of senators. - Sapa-AFP