WASHINGTON – As President Donald Trump ramps up his reelection for 2020, he is resurfacing an unsubstantiated gripe from 2016: That voter fraud cost him support.

At rallies and on Twitter, the president has renewed calls for voter ID laws, revisited assertions that a large number of people voted fraudulently and signaled that, until those issues are resolved, other pending election measures are going nowhere.

Trump hammered the theme during a New Hampshire rally this week, repeating a statement – dismissed by his allies and critics alike – that thousands of people fraudulently voted for Democrat Hillary Clinton there. She won the state by fewer than 3,000 votes.

“It’s also time for Democrats to join with us to protect the sacred integrity of our elections by supporting voter ID,” Trump said to robust applause in Manchester.

Days earlier, Trump wrote in a tweet that no other election security measures pending in Washington should move forward unless voter ID laws are addressed first. Voter ID laws have drawn sharp opposition from Democrats who say that voter fraud is uncommon and that requiring IDs could disenfranchise some voters.

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“No debate on Election Security should go forward without first agreeing that Voter ID must play a very strong part in any final agreement,” Trump posted on Twitter this week.

Popular vote

Trump's latest assertions echo those he made in 2017, when he explained his popular vote loss to Clinton by repeatedly suggesting millions of people voted fraudulently for his Democratic opponent. The president never provided evidence for the statement, which drew pushback from Republican and Democratic state election officials.

He raised a similar argument Thursday as he traveled to New Hampshire.

"New Hampshire should have been won last time, except we had a lot of people come in at the last moment, which was a rather strange situation," Trump said before the rally. "Thousands and thousands of people coming in from locations unknown."

Neither Trump nor his aides have backed up that assertion.

Trump created a commission in 2017 to study the issue of voter fraud but abandoned it months later amid internal disputes and rebukes from state election officials. Maine Secretary of State Matthew Dunlap, a Democrat who served on the disbanded commission, wrote that the panel's evidence of voter fraud was "glaringly empty."

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The president put the issue on a back burner for a while.

The reincarnation of his allegations comes as Democrats press Senate Republicans to take up a series of provisions they say will improve voting systems. The Democratic-led House approved legislation in June that would require states to have paper ballot backups. The measure also would require voting systems to be manufactured in the USA.

Democrats initiated the effort in response to special counsel Robert Mueller’s report in April. Mueller wrote that the Russian government interfered in the 2016 election in a “sweeping and systematic fashion.” Noting the measure received only one Republican vote on the House, Senate Majority Leader Mitch McConnell dismissed the bill as a partisan effort intended “to rewrite all kinds of the rules of American politics.”

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Democrats have long questioned the need for voter ID requirements, saying they hearken to efforts to suppress minority turnout.

"Donald Trump can’t win an election based on his ideas, so he has to suppress the vote to win," presidential candidate Sen. Bernie Sanders wrote on Twitter. "What a coward."

Voter ID

Thirty-five states, including New Hampshire, have some form of voter ID law in place, according to a National Conference of State Legislatures review this year. Those laws are wide-ranging: Some require a photo ID; others allow poll workers to vouch for a voter or let a voter sign an affidavit of identity if he or she doesn't come to the polls with an ID.

Many of those laws have faced legal hurdles. Wisconsin's voter ID law has been mired in court challenges for years, for instance. A lawsuit filed in 2015 over an Alabama voter ID law is pending in a federal appeals court.

"Republicans in 2011 did it with the express purpose of driving down voter turnout," said Jay Heck, longtime executive director of Common Cause Wisconsin, where Trump won in 2016 with almost 23,000 votes.

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Max Feldman, counsel for the voting rights and election program at the Brennan Center for Justice, said voter ID laws are more harmful than the problem of voter fraud that supporters say they are attempting to fix. Since the disputed 2000 election, government and private investigations have found no substantial voter fraud.

"As we get closer and closer to the 2020 election, this issue and the attempt to gin up false concern about in-person voter fraud will have greater and greater salience," Feldman said. "It's critical that people understand that in-person voter fraud has not proven to be a significant problem in our elections."

New Hampshire Gov. Chris Sununu, a Republican ally of Trump's, initially questioned the president's claim of mystery voters after the 2016 election. But Sununu, who attended the Trump rally Thursday, went on to sign laws that tightened voter eligibility in New Hampshire. One requires residents who move there within a month of an election to document that they intend to stay.

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Trump and others said Americans are used to pulling out their IDs. Studies on the impact the laws have on disenfranchisement have drawn mixed conclusions.

"The idea that requiring an ID is somehow voter suppression is truly one of the strangest falsehoods ever perpetuated by the Democratic Party," Rep. Dan Crenshaw, R-Texas, a Trump ally, posted on Twitter this week. "It defies logic for any normal American who uses their ID. Every. Single. Day."

Opponents of the laws acknowledge that for many Americans, that is true, but it's not the case for everybody. Groups such as Common Cause try to ensure that people obtain an ID needed to vote.

"There are people who are properly registered in this state who, through no fault of their own, have no ID and may have problems getting one," said Bob Phillips, executive director of Common Cause North Carolina. "It's regrettable that voting has become almost a partisan issue."