As the struggle over dimpled chads and voting machines grinds on in the courts, evidence is emerging that the US presidential race was irrevocably tainted before a single ballot was cast - by the systematic and unconstitutional denial of voting rights to thousands of black Floridians.

Across Florida, black residents who had taken part in earlier elections without any problems went to vote on November 7 to find a bewildering array of hurdles between them and the ballot box. For many, the day's events were a reminder that Florida is an integral part of the deep south, with a long record of segregation and resistance to black voting rights.

The state is under investigation by the justice department for infringing the rights of its minority citizens, but cases of black disenfranchisement have played almost no role in the challenge by the vice-president, Al Gore, to the election results. Ballots cast can be recounted and yield quick results, while votes denied are difficult to measure and hard to claim. But in the longer term, they have far graver implications for US race relations and the health of the nation's democracy.

In most cases investigated by the Guardian, the obstacles to black voting rights were clerical and administrative. In a handful of instances, however, they were less subtle.

On election morning, Darryl Gorham was driving some neighbours to vote in Woodville, outside Tallahassee. They turned a bend in the road about a mile before the polling station and came across a scene straight out of the segregation era.

Roadblocks

"There were four Florida highway patrolmen standing in the middle of the street, Mr Gorham said. "They were stopping everybody. They had seven or eight cars stopped on the side of the road and waiting. They inspected the headlights, tail-lights, indicators, licence, registration, tags, everything ... I've lived in Florida most of my life, but I have never ever seen a roadblock like that."

Mr Gorham is convinced that the white policemen were trying to slow down the flow of black voters in a historically tight election. He said: "It took maybe 15, maybe 20 minutes. But many people were taking time out from work, or going to work, and it was making them late. Some just turned round and went back."

Major Ken Howes, a spokesman for the Florida Highway Patrol, said the four policemen had set up the checkpoint without authority from senior officers. An internal investigation has been launched but Major Howes insisted the sergeant in charge had not intended to affect the vote.

Robert Chamber, a black resident who lives nearby, is sceptical of the claims of ignorance. He believes the checkpoint's message was quite clear. "It is putting fear in people's hearts," he said. "It means: 'We'll catch them before they get there.' The racism here may be underground but it's strong. There are places around here we just know not to go."

There is some hard evidence to back up Mr Chamber's fears. According to a study by the Southern Poverty Law Centre, the largest concentration by far of neo-Confederate white supremacist groups such as the League of the South is centred on the Florida panhandle and the state's western coast.

Marvin Davies, a veteran of the 1960s civil rights struggle, said: "Florida has always been a microcosm of hate ... Both racism and hate are a very viable part of this culture."

Woodville was not the only alleged police intimidation in Florida. However, by far the greatest damage to minority rights appears to have been inflicted not by men in uniform, but by bureaucrats in suits, quietly and almost invisibly, months before the election.

During the presidential campaign, it became clear that Florida would be piv otal and that civil rights groups were making unprecedented efforts to mobilise minority voters behind the Democrats. Under the banner of an anti-fraud campaign, Governor Jeb Bush, the brother of the Republican presidential candidate, and his now-famous secretary of state, Katherine Harris, implemented a series of administrative steps which may well prove to have swung the election.

In June, the division of elections in Ms Harris's office drew up a list of more than 700,000 Floridians permanently disqualified from voting - more than any other state - because of a criminal past, and sent it to county election supervisors.

The idea was to enforce strictly an 1868 law disqualifying felons and ex-felons from voting for life. The law was originally part of the southern backlash against voter registration among freed slaves after the civil war, and was based on the assumption that black residents got in trouble with the law more often than their white counterparts.

That assumption holds true today, in a state where African Americans make up 13% of the general population but 55% of prison inmates. According to Human Rights Watch, around a third of African American men in the state were disqualified from voting because of a past conviction, mostly resulting from the "war on drugs" that has been raging in urban America for two decades.

But Ms Harris's list went further than simply upholding a 19th-century law. It included several thousand people who should not have been disqualified, either because they had gone through the arduous process of having their rights restored or because they had never been convicted of a felony in the first place.

The list was so riddled with errors that Palm Beach and Duval election boards simply ignored it, leading to Republican allegations that more than 300 ex-felons had voted in those counties. But their numbers appear to be far outweighed by those wrongly disenfranchised elsewhere.

When he was 23, Wallace McDonald fell asleep on a bench in Tampa waiting for a bus. He was arrested for vagrancy and obliged to pay for his misdemeanour by working on a municipal rubbish truck. Disgusted with his sentence, the young McDonald walked off the job, an offence for which he was fined $30.

That was in 1959. Forty-one years on, Mr McDonald received a letter from the Hillsborough County election supervisor, Pam Iorio, informing him that as an ex-felon his name had been removed from the voters' roll.

"I could not believe it, after voting for all these years since the 50s, without a problem," he said, pointing out that even by Florida's harsh standards his offence did not amount to a felony. "I knew something was unfair about that. To be able to vote all your life then to have somebody reach in a bag and take some technicality that you can't vote," Mr McDonald said. "Why now? Something's wrong."

He is in good company. The Rev Willie Dixon received a full pardon for drug offences in 1985, and has since become a youth leader and bible preacher, a pillar of the Tampa black community who has voted in every presidential election. Until he received one of Ms Iorio's letters.

Kelvin King never received a letter. He was also released in 1985, after becoming another statistic in the drug war. He got his registration card and had voted in the three presidential polls held since his release from jail. This November, he was ejected from a polling station after his name turned up on the blacklist.

"The lady on the desk just told me I was a felon. It was a bit of a shock," Mr King said. "I suppose I was disgusted at myself for what I had done in the past, but I assumed it had been taken care of."

In her Tampa offices, a defensive Ms Iorio, a Democrat, pointed the finger of blame at Tallahassee. "Yes, there were errors on the list," she said. "There were instances of mistaken identity and people who should not have been on it. Something doesn't work right in the system."

But the county election supervisor defended her use of Ms Harris's list. Anyone wrongly listed as a felon had ample opportunity to appeal, she argued.

Mr Dixon did manage to have his criminal taint removed but Mr McDonald was not so fortunate, despite the best efforts of his lawyer. Mr King never had a chance.

It is not just ex-convicts who found themselves excluded. Civil rights groups have been inundated with complaints from mainly black voters that they had not found their names on the voters' roll.

Again, many of the disenfranchised appear to have fallen prey to the Florida government's zeal in applying electoral regulations. Under federal law, states can purge citizens from the rolls if they fail to participate in two consecutive federal elections and if letters sent to their address are returned.

But once more, Ms Harris's office appears to have gone beyond the letter of the law, ordering a comprehensive purge of the rolls in October, provoking several hundred complaints from would-be voters who said their names had been erased despite a consistent voting record.

Discrimination

Once again, the vast majority of those complaining are black. It may be that low-income minority families are less settled and more likely to change address but community leaders are convinced their disenfranchisement reflects deeper discrimination. They can point to the case of Kandy Wells, a black woman who registered in Tampa on the same September day as her white husband. He received his voter's card two weeks before election day. Mrs Wells is still waiting for hers.

"You've got to remember that only 40 or 50 years ago blacks couldn't vote," she said. "Things like this have been happen ing in Florida all along. It's just that this time it's so close and they got caught."

Black voters across the state have also claimed that they were subjected to more stringent identity checks than their white neighbours, leading to longer delays. In Miami, Haitian immigrants were routinely denied their right to bring an interpreter to the polling booth to help translate the ballot.

In theory, the "errors" should have been corrected on election day, but in many places officials were so overwhelmed by the problem that the instant appeals mechanism collapsed. In Tampa, lines to Ms Iorio's office were overwhelmed as voters tried in vain to call from polling stations to have themselves reinstated. Again, low-income minority neighbourhoods were worst affected, magnifying the impression that Florida was practising selective disenfranchisement.

Governor Bush's administration has dismissed claims of discrimination as yet another Democratic ruse aimed at undermining the election result. And the De mocratic party is clearly reluctant to pick up the banner of its black supporters.

But the angry mood among black Floridians is unlikely to be dispelled without an examination of what happened on November 7 and beforehand. It is a reckoning that is likely to last far longer than the recounts squabble, because it lies at the heart of black experience in the south.

In Marvin Davies's eyes, the battle over the Florida election is simply the continuation of the earlier, bloodier struggles of the 1950s and 1960s.

"When you go into that ballot box, the black man has the same power as the white man, so the white man will use all his money and all his power to stop the black man getting there," Mr Davies said.

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Timeline - when will America decide?

Election glossary

Graphic: Know your chad

Interactive

Results declared, state by state

Audio Julian Borger in Tallhassee

Local media

Miami Herald

Tallahassee Democrat

Palm Beach Post

Sun Sentinel

Key document

Download the previous Florida supreme court ruling (pdf file)