One year after the 2016 presidential election, rights groups say voter suppression laws have only gotten worse in the United States.

Voters in a dozen cities and states went to the polls on Tuesday to vote on everything from city mayor to state governor.

But rights groups warned that many faced requirements to prove their identity that did not exist a year ago.

In Missouri, an amendment to the state constitution required voters to present proof of identity before casting a ballot.

Voting rights advocates said the measure, passed by referendum last year, caused confusion at the polls.

"We have people at the polls in this state conducting exit surveys, asking voters about what kind of information they received about this new law, and we're seeing that a lot of people are greatly uninformed," said Denise Lieberman, a senior attorney at the national office of the Advancement Project, a civil rights organisation.

"When people don't know how to navigate new rules, they are confused, they are intimidated, and they stay home," Lieberman told Al Jazeera.

Other states that passed laws in the past year that make it more difficult to vote include Arkansas, Iowa, North Dakota, Texas, and New Hampshire.

But efforts to restrict voting rights are not new to 2017.

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Some point to a wave of measures restricting access to the ballot, which disproportionately affected Democratic-leaning voters, in the lead-up to the 2016 presidential election, as an explanation for Donald Trump's surprise win.

Yet, one year later, voting rights advocates say that attempts to limit the franchise have only intensified, and are being backed by the current administration.

"There's certainly more energy behind them, and you have this sad and unfortunate federal government imprimatur on the top of them," said Ronald Newman, director of strategic initiatives at the American Civil Liberties Union (ACLU).

"Whereas two years ago or four years ago, when a state made moves to restrict access to the ballot, you had the federal government coming in - through the Department of Justice, through the civil rights division - saying, 'hey, stop this'," Newman told Al Jazeera.

"Well, you've seen a big slip on that front."

Moves by the Trump administration

The Trump administration has supported claims that voter fraud is rampant.

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Such arguments are usually offered as a justification for tougher registration and identification requirements.

After winning last year's election, Trump tweeted that his margin of victory would have been larger "if you deduct the millions of people who voted illegally".

The president formed an Advisory Commission on Electoral Integrity after claiming, without evidence, that 3 to 5 million illegal votes had been cast in the 2016 election.

Headed by Vice President Mike Pence, the commission has sought to collect voter data from states, which civil rights groups fear the administration could misuse to validate claims of widespread illegal voting.

"If the commission has large amounts of data, and it uses that information in a way that … does not represent sound methodology, they could substantially overestimate or overstate the extent of illegal voting," said Jonathan Brater, democracy counsel at the Brennan Center, a public policy institute that opposes voter ID laws.

For example, the commission could overestimate double votes by matching voters only by first name, last name and date of birth, which produces large numbers of false matches, Brater said.

Two years ago or four years ago, when a state made moves to restrict access to the ballot, you had the federal government coming in - through the Department of Justice, through the civil rights division - saying, 'hey, stop this'. Ronald Newman, ACLU

Trump's Department of Justice (DOJ) has signalled that it might pressure states to purge voter rolls.

States are responsible for maintaining lists of eligible voters, removing residents who die, move away or otherwise become ineligible to vote.

Research by conservative watchdog group Judicial Watch has indicated that millions of ineligible voters remain on state rolls. The DOJ sent states a letter last summer inquiring about voter roll maintenance practices.

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But purges are often sweeping and clumsy, voting rights advocates say, and remove large numbers of legitimate voters.

"When states and local jurisdictions conduct voter purges without the appropriate safeguards, they can sweep up large numbers of eligible voters, who can then be removed from the rolls without the proper notification and waiting period," said Brater.

This "can then result in disenfranchisement when they show up to the polls only to find that they have had their voter registration cancelled".

The Trump administration has also intervened in legal disputes over individual state voter ID laws, as it did recently on behalf of Texas.

After a federal judge ruled against the latest version of Texas' voter ID law, the DOJ threw its support behind the law, which requires voters to show identification.

An appeals court reversed the lower court's decision, permitting identification requirements in Tuesday's election.

A range of barriers

Barriers to voting vary state-by-state. Before the 2016 election, a federal court allowed Wisconsin to implement its 2011 voter ID law, which required voters to present a certified document proving their identity before they could cast a ballot.

A study by the University of Wisconsin estimated that the measure prevented nearly 17,000 registered voters from going to the polls in 2016.

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North Carolina passed a 2013 law that limited voting options on which the state's black citizens disproportionately relied, including same-day voting, early voting and out-of-precinct voting.

In July 2016, a federal appeals court struck down most of the law's provisions, saying that they targeted "African Americans with almost surgical precision".

Three US states, including the key swing state of Florida, permanently remove voting rights from anyone convicted of a felony - a measure that disenfranchises more than 10 percent of all Floridians, reversible only by order of the governor.

In 2011, Florida Governor Rick Scott signed into law a set of rules making it more difficult for ex-felons to apply for restoration of their voting rights.

Conservative groups say that voter ID laws and registration overhauls are needed to combat a scourge of voter fraud.

As evidence, the Washington, DC-based Heritage Foundation maintains a database that lists 1,088 instances of voter fraud.

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But rights groups say that voter fraud and voting by non-citizens remain vanishingly rare.

An analysis by the Brennan Center found that the Heritage Foundation's database includes "just 10 cases involving in-person impersonation fraud at the polls" and "41 cases involving non-citizens registering, voting, or attempting to vote" – the types of fraud that stricter laws are intended to address.

Instead, advocates say that voting restrictions disproportionately affect poor, working class and minority communities, which struggle to meet the requirements imposed by such laws.

Minority voters are less likely to possess valid IDs and face significant financial and logistical barriers to obtaining them, said the Advancement Project's Denise Lieberman.

"The barriers really add up exponentially," Lieberman said.

What's next?

The fight over voting rights will soon reach the Supreme Court, which is scheduled to hear arguments about whether Ohio may remove voters from its rolls who have not voted for at least four years.

The ACLU's Newman also said that the Trump administration might target the National Voter Registration Act, which protects common methods used to register voters. Changing the 1993 law would require Congress to pass legislation and could allow states to limit registration options.

"What they want to do is be in a position to create more burdens and obstacles in that process, and they need to change the law in order to do it," Newman said.