Civil rights groups say a tangle of Republican-backed “voter suppression” laws enacted since 2010 probably helped tip the scale for Republican nominee Donald Trump in some closely contested states on election night.

“When we look back, we will find that voter suppression figured prominently in the story surrounding the 2016 presidential election,” said Kristen Clarke, the president and executive director of the Lawyers’ Committee for Civil Rights Under Law.

Fourteen states had restrictive new voting laws on the books for the first time in a presidential election this year, according to the Brennan Center for Justice at NYU School of Law: Alabama, Arizona, Indiana, Kansas, Mississippi, Nebraska, New Hampshire, Ohio, Rhode Island, South Carolina, Tennessee, Texas, Virginia and Wisconsin.

The laws included a mix of photo ID requirements for voters, cuts to early voting opportunities and curbs on voter registration activity.

The laws, which were presumably enacted as a safeguard against voter fraud, began to spread nationally after the 2010 midterm elections, when large numbers of Republicans were swept into state offices.

Since then, 10 states have imposed stricter voter ID laws, seven made registration more difficult, six have cut early voting opportunities and three have made it harder to restore voting rights to people with criminal convictions, according to the Brennan Center.

The center charges that race and partisanship are behind many of the laws, which have been found to disproportionately affect voters who traditionally vote Democratic: minorities, the poor, college students and other young voters..

In addition to systemic barriers, voters faced individual obstacles on Election Day, Clarke said during a news briefing on Thursday. The problems included long lines at polls, voters’ names not appearing on registration lists, a lack of polling place assistance for foreign-language speakers and “poll workers who requested strict photo ID in states where no such ID was required.”

Groups that monitored Tuesday’s election “have documented beyond any doubt that voter suppression and a conscious effort to shave off 1 or 2 percent of the vote in key states, in all likelihood, influenced the outcome of this election,” said Wade Henderson, the president of the Leadership Conference on Civil and Human Rights.

In addition, activists complained of large-scale registration purges of inactive voters and reductions in the number of places where people could cast ballots.

A report by the leadership conference found that voting locations were reduced in about 43 percent – or 165 – of 381 counties that were previously covered by Section 5 of the Voting Rights Act. The result: There were 868 fewer sites in which to cast a ballot in those jurisdictions with histories of discriminatory voting practices.

Conservatives concerned about voter fraud say the changes were not targeted at minorities.

Robert Knight, a senior fellow at the conservative American Civil Rights Union, told McClatchy in October: “We frankly think that’s an absurd charge . . . that somehow having clean rolls and requiring things like voter ID and even proof of U.S. citizenship somehow suppress the vote of minorities.”

Section 5 of the Voting Rights Act required the U.S. Department of Justice to preapprove changes to voting rules in nine states with long histories of voting discrimination.

But after nearly 50 years, the U.S. Supreme Court voided the “pre-clearance” requirement in June 2013, ruling in Shelby County v. Holder that an invalid formula had been used to determine which jurisdictions should be subject to the provision.

The decision basically gutted the federal pre-clearance program. It also severely limited the Justice Department’s ability to dispatch special election observers with the authority to monitor activity inside polling places.

Civil rights groups said the ruling opened the door for state and local governments to enact a flurry of controversial voting restrictions – like poll closures – without the threat of federal vetting for their discriminatory impact.

In a briefing with reporters last week, Nancy Zirkin, the director of public policy at the leadership conference, called the poll closures “a pernicious tactic for disenfranchising voters of color” because they’re often done quietly, late in the election season, “making pre-election intervention or litigation virtually impossible.”

That lack of transparency means voters don’t always know why or when their polls have closed or relocated. “Nor do we have any idea how these moves affect minority voters,” Zirkin told reporters.

Henderson said the problems were proof that Congress needed to restore the Voting Rights Act to assure that all voters’ rights were protected.

Although it’s unlikely to happen, Henderson said he would ask House Speaker Paul Ryan, R-Wis., and Senate Majority Leader Mitch McConnell, R-Ky., to do address the matter in the lame-duck session of Congress before new members are sworn in.