In 2000 it was hanging chads and black disenfranchisement; in 2004 it was voter purges and electronic tampering. The familiar legal dance has started again in 2008, this time around the issue of voter-registration.

The row is over the registration activities of a non-profit group, ACORN, which Republican officials and the McCain campaign say is a radical organisation linked directly to the Democratic nominee, Barack Obama.

The Republican National Committee spokesman, Danny Diaz, went so far as to label ACORN a "quasi-criminal group" last week, after party members in several states accused it of committing electoral fraud during its voter registration activities.

Many of the charges focus on Ohio, where a federal appeals court yesterday ordered the state’s top election official to set up a system by the end of the week to verify the eligibility of newly registered voters and make the information available to the state’s 88 county election boards.

On Monday, election officials in Ohio’s most populous county asked a prosecutor to investigate multiple registrations by four people who signed up through ACORN.

One voter said he signed 73 voter registration forms over a five-month period.

Yesterday the Buckeye Institute, a conservative think tank in the state, filed a lawsuit against ACORN alleging that the group is engaging in a pattern of corrupt activity that amounts to organised crime and calling for its dissolution.

But ACORN, a community organising group which has worked for 40 years on issues such as low-income housing, voter registration, and the minimum wage, has dismissed the charges as ludicrous.

"It's pretty shocking that anyone would say such a thing," said Bertha Lewis, interim chief organizer for National ACORN.

In a news conference yesterday, ACORN spokesman Kevin Whelan insisted that any irregularities were isolated incidents and were rooted out before making it onto the electoral roll.

“The vast, vast majority were dedicated workers,” he said. “They did something remarkable in bringing all these new voters.”

In Ohio, a key swing state, Barack Obama told reporters yesterday that the group’s registration problems should not be used by the Republicans as an excuse to keep voters from turning out on Election Day.

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