President Trump’s years-long efforts to allege widespread voter fraud in U.S. elections largely have no basis in fact, but he is harping on one claim in particular in recent days as states ramp up efforts to allow mail-in voting amid coronavirus concerns.

Election experts say “harvesting” is a loaded term, with some preferring ballot “collection.” The political debate is far from settled over whether allowing collection of mailed ballots is a bad thing, and it doesn’t always break down along party lines.

Let’s explain.

What is ballot collection or harvesting?

It’s a practice in which a voter fills out an absentee ballot, seals it in an envelope and does all the required security checks, like signing the back of the envelope so election experts can verify who voted. Then they entrust it to another person, who drops off the ballot at a mail center or ballot drop-off location.

The practice is allowed in many states. But why would you want to do it?

“From a voter’s point of view, it may be taken as a kindness if someone offers to mail in or drop off a voted ballot [in its signed envelope],” writes Wendy Underhill, director of the elections and redistricting program at the nonpartisan National Conference of State Legislatures, especially when vulnerable populations are asked to stay at home as much as possible during a pandemic.

From a campaign’s point of view, it’s a way to ensure voters who requested absentee ballots actually turn them in. In states where doing this is legal, campaigns can target those voters and go to their door and ask them whether they want help mailing in their completed ballot. Campaigns see it as another way to get out the vote.

Political operatives from both sides routinely do it. Democrats used it with particular success in California in 2018.

California passed a law in 2016 allowing a third party to collect ballots. Democrats implemented ballot collection programs there that became so successful that, after the 2018 midterms, Republicans attributed their losses in the state in part to those efforts. The Washington Post’s Amy Gardner reported last year that while Republicans were publicly claiming that Democrats’ ballot collection efforts in California could lead to fraud, they were privately strategizing about how to match them in future elections.

The fraud potential

The potential for fraud comes in when you raise the question about the collector’s intentions. Could they be motivated not to deliver the ballot once they collected it, especially if they are of a different political party than the voter?

In a 2018 congressional election in North Carolina, a political operative for the Republican candidate was charged with crimes related to an alleged scheme to illegally collect absentee ballots before turning them in. The election results were thrown out after this scandal came to light.

But what’s alleged to have happened in North Carolina is different from legal ballot collection, which requires the ballot to be filled out and sealed before it’s collected. So it would be difficult for someone collecting ballots to change the actual vote.

In California, campaigns can legally go door-to-door as often as they want and offer to collect the filled-out ballots and drop them off to election officials. “However,” California’s voting law handbooks says, “the designated person cannot interfere with the ballot’s return to the elections official.”

Trump’s more recent descriptions of people “grabbing” or “robbing” ballots from mailboxes are not based on any known evidence. The person has to consent to have their ballot be turned in by someone else. What Trump describes would be theft.

The debate over whether to allow ballot collection

In recent years, states controlled by both parties, especially out West, have limited how many ballots third parties can collect and modified the rules for them, Underhill says.

California legalized ballot collecting in 2016. Secretary of State Alex Padilla has characterized it as “giving voters the power to decide who they most trust to return their vote-by-mail ballot for them if they so choose.” But California has since made it illegal to get paid per ballot collected and for employers to ask employees to bring their ballots into their workplace.

Arizona says no one other than a family member, household member or caregiver can return your ballot. Republicans in Congress have pushed for the same federal restrictions. And Montana limited the amount of ballots people can collect and drop off to six.

Other ideas include tracking ballots sent by mail to make sure they get sent to the right place no matter who collected them, or for state governments to provide prepaid postage so people don’t feel the need to hand off mailing their ballot to someone else. (Though that can get expensive, and states are already crunched for cash as they figure out how to accommodate an expected surge in absentee ballots this year.)

For now, ballot collection seems like a practice that’s here to stay in states where it’s legal. But Trump is pushing it to the top of the list of conservatives’ concerns about conducting more elections by mail this fall.