Barack Obama's White House campaign claims desperate Republicans are waging a nation-wide campaign, orchestrated with John McCain's staff, to intimidate voters and depress turnout in next month's presidential election.

Top aides to the Democrat battled back against what they called a Republican "smokescreen" over a liberal advocacy group called ACORN, which is under investigation in several states over allegations of voter registration fraud.

The group released a video, set to the song You've Lost That Lovin' Feelin', showing Senator McCain warmly greeting its activists at a February 2006 event in support of immigration reform.

Senator Obama says his own ties to the Association of Community Organisations for Reform Now (ACORN) went no further than legal work he did with the Justice Department for ACORN against the state of Illinois in the mid-1990s.

"As an elected official I've had interactions with them," the Illinois Senator told reporters in Ohio.

"But they're not advising the campaign. We've got the best voter registration turnout and volunteer operation in politics right now, and we don't need ACORN's help," he said.

The McCain campaign is airing a 90-second ad alleging close and enduring ties between Senator Obama and ACORN, which it says had bullied banks into extending the kinds of subprime mortgage loans at the heart of the US financial crisis.

The group boasts of gathering the names of 1.3 million mostly non-white, low-income voters in 21 states in the most successful voter registration drive in US history.

But many of the names are said by conservatives to be duplicated, or of famous sports stars, or of cartoon and movie characters.

"If left uncorrected, these numerous investigations and accusations of voter fraud with ACORN could produce a nightmare scenario on election day," Senator McCain's campaign manager Rick Davis said in a statement.

"It is our hope that the Obama campaign joins us in our efforts to prevent voter fraud prior to election day."

'Repression and intimidation'

On MSNBC television, ACORN spokesman Scott Levenson blamed any problems on rogue canvassers and attacked Senator McCain's "denomination of this advocacy group that does work for the most powerless of our society."

Senator Obama's campaign manager David Plouffe says ACORN is in no way involved in his own voter registration program, and says the allegations are a Republican attempt to divert attention from their own "suppression" tactics.

"A lot of noise they're trying to create here is a smokescreen because we have no doubt that their effort towards repression and intimidation is going to be unprecedented," he said.

Mr Plouffe says Senator McCain and the Republicans have nothing to offer on the stricken US economy and suffered a "huge inspiration gap," and so were resorting to trickery to suppress Democratic turnout in swing states.

He says there are now more than 9 million voters newly registered for the November 4 election and Democratic registrations are outpacing Republican ones by four to one.

"There's a long history to Republican efforts to whip up fear about the electoral process," the Obama campaign's general counsel Bob Bauer said, promising a "ferocious" Democratic response in the courts.

He listed reports that Republican bosses in one Michigan county were using lists of foreclosed homes to throw their former owners off the rolls.

In Ohio, Republicans are now attacking a procedure they themselves initiated for the 2004 election allowing voters to register and cast an absentee ballot on the same day.

Mr Bauer rejects the McCain campaign's accusation that Obama operatives had paid $US800,000 to ACORN to register voters in Kansas, insisting cooperation with the group stopped at joint canvassing efforts.

"It's a lie and the repetition of the lie won't make it true. We have never paid ACORN for any registration purposes and they know it," he said.

Mr Plouffe says that as in 2004, state Republicans were hiring burly individuals "with law enforcement backgrounds" to work as nominally independent monitors at polling stations.

"We think this is a highly cynical effort they're engaged in here," he said.

- AFP