ATLANTA (AP) — Changes to the way millions of Americans voted this year contributed to record turnout, but that's no guarantee the measures making it easier to cast ballots will stick around for future elections.

Republicans in key states that voted for President-elect Joe Biden already are pushing for new restrictions, especially to absentee voting. It's an option many states expanded amid the coronavirus outbreak that proved hugely popular and helped ensure one of the smoothest election days in recent years.

President Donald Trump has been unrelenting in his attacks on mail voting as he continues to challenge the legitimacy of an election he lost. Despite a lack of evidence and dozens of losses in the courts, his claims of widespread voter fraud have gained traction with some Republican elected officials.

They are vowing to crack down on mail ballots and threatening to roll back other steps that have made it easier for people to vote.

“This myth could not justify throwing out the results of the election, nor can it justify imposing additional burdens on voters that will disenfranchise many Americans,” said Wendy Weiser, head of the democracy program at the Brennan Center for Justice at the NYU School of Law.

An estimated 108 million people voted before Election Day, either through early in-person voting or by mailing or dropping off absentee ballots. That represented nearly 70% of all votes cast, after states took steps to make it easier to avoid crowded polling places during the pandemic.

A few states sent ballots to every registered voter while others dropped requirements that voters needed a specific excuse to cast an absentee ballot. Many states added drop boxes and expanded early voting options.

The changes were popular with voters and did not lead to widespread fraud. A group of election officials including representatives of the federal cybersecurity agency called the 2020 presidential election the “most secure” election in U.S. history, and U.S. Attorney General William Barr told The Associated Press there had been no evidence of fraud that would change the outcome of the election.

Nevertheless, Republicans in Georgia have proposed adding a photo ID requirement when voting absentee, a ban on drop boxes and possibly a return to requiring an excuse for mail voting, such as illness or traveling for work on Election Day.

Early supporters of the ID requirement include Gov. Brian Kemp and Secretary of State Brad Raffensperger, Republicans who were criticized relentlessly by Trump for failing to back his fraud claims after losing in Georgia. A top deputy for Raffensperger has said the ID requirement would boost public confidence and refute any future claims of fraud.

The state's two U.S. Senate runoffs next month will take place under current law, which requires local election officials to verify signatures on absentee ballots.

In Pennsylvania, Republican lawmakers have been writing legislation to address what they claim are problems with the 2020 election and mail voting in particular, even though courts and elections officials have found no evidence of widespread problems.

“We’d like to tighten it up as soon as we can,” said Pennsylvania Senate Majority Leader Kim Ward.

Republicans hold majorities in both legislative chambers, and their support was instrumental in a year-old state law that expanded mail voting to all registered voters. One bill being discussed would go so far as to repeal that law and force voters to state an excuse to receive a ballot in the mail.

Previous elections have shown that voters appreciate mail voting, no matter their party affiliation. Republican candidates down the ballot did very well this year, even as a record 81.2 million voters cast their ballot for the Democrat in the presidential race.

In Michigan, Republicans held every congressional seat and kept control of the legislature despite Trump losing the state. Yet Republicans still held a legislative hearing in which Trump's lawyers argued there were widespread irregularities without explaining how these somehow affected only the presidential race but not other contests.

“Just like we have seen a lot of legislators making ill-advised decisions to hold hearings that ended up being more political theater than policy debates, we can similarly expect legislators to further this hyper-partisan agenda to restrict the vote,” said Michigan Secretary of State Jocelyn Benson, a Democrat.

Benson said lawmakers should instead look to the high turnout for the presidential election as a guide to improving what worked and then make changes sought by elections officials, such as providing more time for clerks to process mail ballots. Michigan does not allow that work to begin until the day before Election Day.

Lisa Schaefer, executive director of the County Commissioners Association of Pennsylvania, said her organization also would like to see lawmakers focus on reducing the strain facing local election officials.

“The more time that we spend in debating other issues, the less time that we have to do something good with changes to the election code,” Schaefer said.

Democrats and voting rights groups have already begun pushing back, saying Republicans should be focused on protecting voter access to the polls and not feeding into conspiracy theories launched by Trump and his allies to undermine the Nov. 3 election.

They say ID requirements accomplish little, but have a high cost.

“It’s a solution in search of a problem,” said California Secretary of State Alex Padilla, a Democrat who was recently tapped to fill the U.S. Senate seat of Vice President-elect Kamala Harris. "It will undoubtedly have the net effect of disenfranchising a lot of people without necessarily improving election security.”

Padilla supports sending registered voters a ballot in the mail.

Voter fraud does happen, but studies have shown it’s exceedingly rare. Numerous safeguards are built into voting systems to ensure that only eligible voters cast a ballot. Election officials say when fraud does happen, people are caught and prosecuted.

Not all Republicans are seeking to add restrictions.

In Ohio, Secretary of State Frank LaRose said his legislative priorities are to expand early voting locations, increase oversight of election vendors, add an online option for requesting absentee ballots and address confusion over drop boxes.

“Ohio’s got a good thing going, but we don’t want to rest on our laurels,” said LaRose, who wants his priorities approved by the Republican-dominated legislature.

Kentucky Secretary of State Michael Adams said the pandemic forced the state to implement early voting, which proved popular among voters of both major parties. The Republican said he thinks it’s likely state lawmakers will create an early voting policy for subsequent elections and has heard of no opposition to that in the GOP-controlled legislature.

“It just makes voting easier,” he said.

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Izaguirre reported from Lindenhurst, New York. Associated Press writers Marc Levy in Harrisburg, Pennsylvania; Ben Nadler in Atlanta; and Julie Carr Smyth in Columbus, Ohio, contributed to this report.

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Associated Press coverage of voting rights receives support in part from Carnegie Corporation of New York. The AP is solely responsible for this content.