This election could be rigged, Donald Trump darkly warned the other day. Maybe he was trying to gin up his supporters. Maybe he was indulging his familiar paranoia. Maybe he was preparing the ground for defeat at the hands of Hillary Clinton on 8 November. Or, just maybe, he deeply believed what he was arguing: that thanks to America’s supposedly inadequate safeguards against ballot box fraud, “we may have people (read Democrats) who vote 10 times” and steal victory from him.

Now the country’s rich lore of alleged election fraud makes it hard to deny that vote rigging does occur, even in this beacon of the free world. And indeed it does. It’s called suppression of turnout, and it’s practised by Republicans, not Democrats.

Two points should be made about US presidential elections. First, they’re a jungle. In reality, they are not one election, but 51 separate elections that are held simultaneously in the 50 states and the District of Columbia. Each state – not the federal government – sets its own voting hours, lays down the rules for registration and early voting, and decides what sort of voting machines and ballot forms it should use (remember Florida’s hanging chads and butterfly ballots in 2000?) And each state, not the federal government, decides what ID a voter must produce before casting a ballot.

People who will flee America if Donald Trump wins Show all 8 1 /8 People who will flee America if Donald Trump wins People who will flee America if Donald Trump wins Miley Cyrus 'God’ he thinks he is the f***ing chosen one or some shit! … Honestly f*** this sh*t I am moving if this is my president! I don’t say things I don’t mean!' Jemal Countess/Getty Images People who will flee America if Donald Trump wins Whoopi Goldberg 'I don’t think that’s America. I don’t want it to be America. Maybe it’s time for me to move you know' People who will flee America if Donald Trump wins Samuel L. Jackson 'If that mother**er becomes president, I’m moving my black ass to South Africa' People who will flee America if Donald Trump wins Raven Symone 'My confession for this election is, if any Republican gets nominated, I’m gonna move to Canada with my entire family. Is that bad? I already have my ticket. I literally bought my ticket, I swear' People who will flee America if Donald Trump wins Cher 'If he were to be elected, I'm moving to Jupiter' People who will flee America if Donald Trump wins Neve Campbell 'I’m terrified. It’s really scary. My biggest fear is that Trump will triumph. I cannot believe that he is still in the game ... [I'll] move back to Canada' People who will flee America if Donald Trump wins Jon Stewart 'I would consider getting in a rocket and going to another planet, because clearly this planet’s gone bonkers' People who will flee America if Donald Trump wins Randy Blythe 'He could just be a clown. If he is the president, though, I am leaving America 'till he's gone'

Second, in an ever more polarised country, split nearly evenly between two major parties with virtually no common ground, even the smallest advantage can make a vital difference. The rule of thumb is that the fewer people that vote in national elections, the better Republicans fare. And how do Republicans make that happen? By tinkering with state laws, and in particular voter ID laws, to make it harder for poorer people and minorities, typically Democrats, to take part.

This sort of thing used to be most prevalent in the South, where Republicans dominate, and where vote suppression, by means of devices such as poll taxes or literacy tests, was nakedly used to perpetuate white supremacy. But in 1965 such abuse was limited by the Voting Rights Act, crown jewel of the civil rights era, that stipulated any changes in voting laws in the certain specified states had first to be approved by the US Justice Department in Washington.

But in 2013 that provision was struck down by the majority-conservative Supreme Court. The Act had achieved what it set out to do, the court decided, so the prior approval clause wasn’t needed any more. The result was predictable. A slew of states with Republican governors and legislatures pushed through laws tightening voter ID laws making it more complicated for black people, Hispanics and others to vote.

Several of these states were southern. But others, such as Ohio, Wisconsin and North Dakota, were not. Sometimes the new rules reflected local culture. Texas has a list of permitted IDs, excluding student cards but including handgun permits.

The most egregious restrictions were brought in by North Carolina. It slashed the permissible period for early voting and banned same-day registration – both popular options among black people – and drastically tightened ID requirements. That North Carolina, once a Republican stronghold, is now a swing state that Barack Obama carried in 2008 (but not in 2012), is, of course, the purest coincidence.

In the past couple of weeks, courts in most of these states have overturned the laws as discriminatory. But appeals are likely before the November vote. Supporters argue that such rules are essential to stamp out voter fraud. In fact, tough ID laws and the like are a solution in search of a problem.

Pace Donald Trump, cases of people voting without being eligible, voting more than once, or impersonating another person, are negligible – and most of these are accidental. One 2014 study documented 31 credible cases of such fraud in all general, state and municipal elections since 2000 – one dodgy vote per 30 million cast. Some way to rig an election. The areas most vulnerable to fraud are absentee voting, tampering with electronic voting systems and old-fashioned ballot-box stuffing – none of which tougher voter ID rules even pretend to tackle.

Trump boasts about watching 'top secret' Iran video

And there are even less subtle methods of suppressing the vote, such as last-minute switches in polling station venues, or a reduction in the number of voting places in areas where black and Hispanic populations are high. If you can’t find out where to vote, or have to queue for hours to do so, why bother? Which is exactly what Republicans hope. But it all boils down to the one same thing: rigging elections.

Belatedly, however, Democrats are realising that two can play at this game. Consider Governor Terry McAuliffe’s move to reinstate the voting rights of some 200,000 convicted felons in Virginia who have served their sentences, or in those hoary words, “paid their debt to society”.

The history of the ban is instructive. It was imposed by the state’s 1902 constitution along with other measures such as a poll tax and literacy tests, specifically to stop blacks from voting, rolling back reforms that followed the South’s defeat in the Civil War. “Discrimination! Why that is exactly what we propose,” said the old southern Democrat and future US Senator Carter Glass, a prime architect of that constitution.

Glass would later become famous as a sponsor of the Glass-Steagall Act of 1933 that separated retail and investment banking, to help restore financial stability after the Wall Street crash. But in 1902 his goal was far less lofty – “to remove every negro voter who can be gotten rid of, legally, without materially impairing the numerical strength of the white electorate”.