WASHINGTON, D.C. — States are expecting an increase in voters wanting to mail in their ballots as the coronavirus pandemic has made in-person voting potentially dangerous. Some people have questioned whether mail-in ballots are secure.

President Donald Trump has repeatedly said voting by mail has a high potential for voter fraud, despite recently casting an absentee ballot in Florida himself. But officials in states that conduct elections entirely by mail say fraud is extremely rare, and they also have measures in place to protect against ballot tampering.

The question for other states is whether, and how quickly, they can ramp up similar protections ahead of November.

Trump and others questioning the security of mail-in ballots do have a recent, high-profile example in North Carolina’s 9th District, where the 2018 election results were thrown out after a Republican political consultant was accused of tampering with absentee ballots.

Hans A. von Spakovsky, manager of the Election Reform Initiative at the conservative Heritage Foundation, said all-mail elections create opportunities for fraud because ballots aren’t cast under the watchful eyes of election officials at polling places.

“The secret ballot disappears with absentee voting,” he said.

Proponents of voting by mail pushed back, arguing that there is little evidence of fraudulent ballots and that no system is perfect.

“If someone really wants to perpetrate fraud, I think they probably could in any system, including voting at a polling place,” said Washington Secretary of State Kim Wyman, a Republican. “So no system is completely free of the potential of fraud.”

Amber McReynolds, CEO of the National Vote at Home Institute and Coalition, said fraud with mail or absentee ballots is “exceedingly rare.” She pointed to Heritage’s own election fraud database, which has documented 206 cases of fraudulent use of absentee ballots since 1991. For the five states that conduct elections entirely by mail, the database has no such cases in Hawaii and Utah, two in Oregon, five in Colorado and six in Washington.

“There’s just no real indication of any kind of widespread or systematic voter fraud,” said Justin Lee, Utah’s director of elections. Lee did not have data on how many ballots have been flagged as problematic.

“Maybe that indicates how little a problem we think it is,” Lee said.

Colorado Secretary of State Jena Griswold said during a recent webinar with the Center for American Progress that her state’s elections are very secure and, when it comes to fraud, “prosecution rates are extremely low.”

Steve Hurlbert, a spokesman for Griswold, wrote in an email to CQ Roll Call that after the 2018 election, officials referred 62 ballots —or 0.0027% of the more than 2.5 million ballots cast —to the state’s attorney general for investigation.

The state evaluated its ballots as part of a project through the Electronic Registration Information Center, which is a coalition of 30 states and the District of Columbia that share voter registration information to ensure their voter rolls are accurate. Member states can request data from ERIC to help identify “improper votes,” or instances where a voter may have voted twice in the same jurisdiction, in more than one jurisdiction, or on behalf of someone who is deceased. The center declined to say how many or which states participated in this program in 2018.

Officials in four of the five completely vote-by-mail states say they have protections in place to verify ballots to protect against fraud. Officials in Hawaii did not respond to requests for comment.

Griswold of Colorado, Wyman of Washington, Lee of Utah and a spokeswoman for the Oregon secretary of state all said the states conduct ballot signature comparisons as one protection. A voter’s signature is compared with others on file, such as a voter registration form or a driver’s license. Officials also noted that paper ballots can be more secure than a ballot cast electronically.

“The great thing about mail ballots is they cannot be hacked,” Griswold said.

Ballots are also sent out with unique bar codes linked to the voter and the ballot, to prevent a voter from casting more than one ballot. States also have secure drop boxes at voting enters and tracking systems so voters can keep tabs on their ballots.

Whether other states have time to ramp up similar protections to contend with an expected coronavirus-driven surge in mail-in ballots likely varies by state and the prevalence of voting by mail.

Louisiana Secretary of State Kyle Ardoin, a Republican, said on a recent press call organized by Democratic senators that roughly 4% of his state’s voters cast mail-in ballots, so transitioning entirely to a vote-by-mail system “is neither prudent nor practical.”

McReynolds, CEO of the National Vote at Home Institute and Coalition, acknowledged that, with less than seven months until Election Day, election officials are facing a time crunch to expand their ability to properly and securely process more mail-in ballots.

“There is time, but time is of the essence,” McReynolds said. “And time is the biggest challenge that election officials face right now.”

McReynolds said there are steps states could take immediately to ramp up ballot protections by building on systems already in place to process absentee ballots.

“It’s just a matter of scaling it,” McReynolds said. Although the states that vote entirely by mail took years —years —to ramp up their systems, she noted these states have also developed best practices for securing ballots that can be shared with other states looking to join them.

Wyman and Lee said they have been in touch with election officials in other states about processes for voting by mail.

“No one has to invent the wheel by themselves here,” Lee said.