Ballot harvesting, or the practice of allowing political operatives and others to collect voters’ ballots and turn them in en masse to polling stations, has drawn bipartisan concerns of fraud from election watchers.

Several states have enacted some restrictions on the practice, while others have expressly allowed it or failed to regulate it at all. According to a 2019 analysis by Ballotpedia, 24 states and the District of Columbia permit someone chosen by the voter to return mail ballots on their own, with nine of those states adding some specific exceptions.

Twelve states outline who specifically can return ballots (i.e., family members or caregivers); and one state explicitly requires only voters can return their ballots. Eleven states establish a limit on the number of ballots that a so-called "harvester" can return.

Imposing restrictions on the practice has led to legal challenges. In Arizona, a federal appeals court upheld a ballot harvesting prohibition, despite a claim that it unfairly discriminated against minorities who might need help filling out their ballots.

Some prominent examples of ballot harvesting have already impacted national politics. In 2016, California Gov. Jerry Brown signed into law AB1921, which legalized ballot harvesting. Previously, only a family member or someone living in the same household was permitted to drop off mail ballots for a voter, but the new allowed anyone -- including political operatives -- to collect and return them for a voter.

HOW BALLOT HARVESTING HELPED DEMS ROUT GOP IN CALIFORNIA

The move apparently led to results. In 2018, despite holding substantial leads on Election Day, many Republican candidates in California saw their advantages shrink, and then disappear, as late-arriving Democratic votes were counted in the weeks following the election. Many observers pointed to the Democrats' use of ballot harvesting as a key to their success in the elections.

“Anecdotally, there was a lot of evidence that ballot harvesting was going on,” Neal Kelley, the registrar for voters in Southern California’s Orange County, told Fox News at the time.

In Orange County -- once seen as a Republican stronghold in the state -- every House seat went to a Democrat after an unprecedented “250,000” vote-by-mail drop-offs were counted, the San Francisco Chronicle reported.

“People were carrying in stacks of 100 and 200 of them. We had had multiple people calling to ask if these people were allowed to do this,” Kelley said.

Orange County Republican Chairman Fred Whitaker said the ballot harvesting “directly caused the switch from being ahead on election night to losing two weeks later.”

EX-CLINTON LAWYER THREATENS TO SUE NEVADA UNLESS IT RESTRICTS BALLOT HARVESTING

Later, in 2019, a GOP operative in North Carolina was arrested related to alleged ballot harvesting there.

“The evidence that we will provide today will show that a coordinated, unlawful and substantially resourced absentee ballot scheme operated in the 2018 general election” in parts of North Carolina’s 9th Congressional District, former state elections director Kim Strach remarked at the time.

The results in the race were eventually thrown out amid concerns of ballot harvesting and other fraud. Republican Dan Bishop won a September 2019 special election for the seat.

RealClearInvestigations has found ballot harvesting is common in other states, including Florida, where harvesters are known as “boleteros," and Texas, where they’re called “politiqueras.”

The issue was again thrown into focus in March, when an ex-Clinton lawyer threatened to sue Nevada unless it relaxed its ballot harvesting rules amid the coronavirus pandemic.

"GET RID OF BALLOT HARVESTING, IT IS RAMPANT WITH FRAUD," President Trump wrote on Twitter on Tuesday. "THE USA MUST HAVE VOTER I.D., THE ONLY WAY TO GET AN HONEST COUNT!"