None of those claims have been proven. But on Tuesday, Trump's "Election Integrity" commission is in New Hampshire to look for evidence.
The commission, led by Kansas secretary of state Kris Kobach, has scheduled a series of presentations
from long-time advocates for stricter controls on voting. Among them: The Heritage Foundation's Hans von Spakovsky, who plans to highlight egregious examples of voter fraud; and the Crime Prevention Research Center's John Lott Jr., who will advocate background checks for voters.
The agenda is light on elections experts who will push back or question the testimony. So Democrats on the panel are preparing rebuttals themselves.
"It could get a little feisty," said Matthew Dunlap, Maine's secretary of state and a Democratic member of the commission.
Kobach himself is already under fire after publishing a Breitbart op-ed
in which he claimed out-of-state voters took advantage of New Hampshire's same-day registration laws and cast fraudulent ballots that tipped the outcome of the state's election in Clinton's favor.
What Kobach left out: Students attending college in New Hampshire are allowed to vote there -- and use
out-of-state drivers' licenses to prove their identity.
"The connectivity between not updating your driver's license address and voter fraud is like saying if you have money in your wallet, you must have robbed somebody," Dunlap said.
He added: "I think it's really reckless to make an allegation like that based on how I know licenses are issued around the country and how elections are conducted. It's an amazing leap to make."
Democrats have long complained that Republican-backed state laws -- including voter ID laws, limitations on early voting, objecting to same-day voter registration and more -- have a disproportionate impact on poorer voters, city dwellers and older voters who have no need to drive and college students. They regard the entire commission as a sham designed to soothe Trump's ego after his unsubstantiated claims that voter fraud is why he lost the popular vote to Clinton.
"Donald Trump created this commission because he was humiliated about losing the 2016 popular vote. Then he tapped Kris Kobach, the king of voter suppression, to lead it. Our election process must be secure, fair and transparent, yet Trump and Kobach are using their sham commission to spread the lie of rampant fraud as a Trojan Horse for voter suppression," said Dale Ho, the director of the ACLU's Voting Rights Project.
Republicans -- particularly Kobach -- have meanwhile argued that state voting rolls that haven't been scrubbed for former voters who have moved or died have created a system ripe for exploitation.
J. Christian Adams, the Public Interest Legal Foundation general counsel who will appear Tuesday, said the organization found 616 instances in New Jersey in which an undocumented immigrant -- most of whom had been up-front about their citizenship status -- had been allowed to register to vote.
"A limited inquiry found that hundreds of noncitizens are documented throughout voter records, typically because a bureaucrat offered them an application. Some were even asked after presenting a green card. That broken system is propped up by an honor code proven repeatedly to fail," Adams said in a statement.
The controversy will kick off before the 10 a.m. ET meeting starts. Jason Kander, the former Missouri secretary of state who has launched the Let America Vote political action committee and chairs a Democratic National Committee voting rights panel, has scheduled a rally and press conference where he is expected to tear into the Kobach-led commission.