by Mira Oberman

TOLEDO, Ohio - With John McCain and Barack Obama already swapping accusations of widespread voter fraud, experts warn that a bitter and protracted fight could ensue if the race to the White House is decided by a narrow margin.

The legal battle over election rules has already made it all the way to the Supreme Court as Republicans fight to block potentially false registrations from being validated and Democrats struggle to prevent voter disenfranchisement.

Compounding the problem is the decentralized US electoral system, which hands often partisan local officials the power to make rules and maintain the voter registration rolls.

"I'm hoping it's not close," said Richard L. Hasen, a professor who specializes in election law at Loyola Law School in Los Angeles.

"I am certain there will be problems on election day."

An estimated nine million new voters have registered for the hotly contested November 4 election, and the Obama campaign says Democratic registrations are outpacing Republican ones by four to one.

The McCain campaign contends that an untold number of those registration forms are false and warns that illegally cast ballots could alter the results of the election and undermine the public's faith in democracy.

Republicans have launched a slew of lawsuits aimed at preventing false ballots from being cast, the most high-profile an attempt to challenge as many as 200,000 of more than 600,000 new registrations submitted in the battleground state of Ohio that was blocked by a Supreme Court ruling Friday.

They point to investigations into whether liberal-leaning community organization ACORN deliberately submitted false voter registrations as proof of "rampant" and widespread fraud which McCain said could be "destroying the fabric of democracy."

But the Obama campaign said this was just a "smokescreen" to divert attention from Republican "plotting" to suppress legitimate votes and to "sow confusion and harass voters and complicate the process for millions of Americans."

Voters whose registrations have been challenged or those who find their names have been removed from the rolls are often required to cast provisional ballots, which are not immediately counted in some jurisdictions and are often rejected due to technicalities.

Meanwhile, a 2007 study by the New York University School of Law concluded that "it is more likely that an individual will be struck by lightning than that he will impersonate another voter at the polls."

"For these problems to be really decisive they have to be within the margin of litigation, which is typically a few thousand votes," Hasen said in a recent interview.

The 2000 election took weeks to resolve as Democrat Al Gore fought Republican George W. Bush all the way to the Supreme Court after Bush won the state of Florida, and thus the election, with a margin of a few hundred votes.

Four years later, Democrat John Kerry conceded defeat despite allegations of widespread voter suppression in Ohio, which handed Bush his second term with a margin of nearly 119,000 votes.

In the meantime, electoral litigation has become part of the standard play book.

The number of lawsuits filed over elections has more than doubled from an average of 94 in the four years prior to the 2000 election to an average of 230 in the six years following, Hasen found in a study published in the Stanford Law Review.

Misinformation has also been used to discourage voters from showing up on election day.

Students in Virginia, Colorado and South Carolina were wrongfully told by voting officials that they could lose their scholarships and their parents would no longer be able to claim them on their income taxes if they registered to vote in their college towns.

The Michigan Department of Civil Rights launched an advertising campaign this week to combat misleading rumors - some started by local officials in mailings to voters - that people would be denied the right to vote if they lost their home to foreclosure, have a criminal record or do not have photo identification.

Such tactics are not new, said Laughlin McDonald, the director of the American Civil Liberties Union's voting rights project.

Despite strict constitutional and legal protections for the right to vote, "the history of the country has been one of flagrant vote denial," McDonald told AFP.

Many of tactics once used to keep blacks from voting in the south - poll taxes, literacy tests, violence and intimidation - have been eliminated.

But some have been adapted, including the practice of purging voting rolls of people likely to vote for the other party by challenging them en masse.

"There's more (attempts at voter suppression) that's been going on in the lead-up to this election than any I can remember," McDonald told AFP.

"The fact remains the people who have the power to make the rules are all too often willing to do so in ways that serve their partisan interests."