President Donald Trump has, at times, justified his campaign against mail-in voting in explicitly partisan terms, claiming Republicans’ electoral chances hinge on whether the practice is allowed.

A new analysis from a Democratic-aligned voting rights group, shared first with States Newsroom, shows he may be right: Eliminating mail-in voting would be more disruptive to Democratic voters than Republicans.

Fair Fight Action, a Georgia-based advocacy group founded by Democratic former state Rep. Stacey Abrams, analyzed vote-by-mail data in seven 2024 swing states and potential battlegrounds for the 2026 midterm elections. 

Records indicated that Democrats voted by mail more often than Republicans.

The partisan differences didn’t swing any battleground states in the 2024 presidential election, all of which Trump won.

But if Trump succeeds in restricting mail voting in the 2026 midterms, which he is attempting through a contentious executive order directing the U.S. Postal Service to enforce new requirements, it could help Republicans win key House and Senate seats as each party seeks a narrow path to a majority in either chamber.

Dems’ mail voting edge

For example, in Michigan, one of the toss-up U.S. Senate races that will determine control, more than 2 million voters cast mail ballots in 2024, according to the Fair Fight analysis. 

Nearly half came from Democrats, while Republicans sent 39%, a difference of about 200,000 votes in Democrats’ favor. That gap represents a smaller number of votes than the margin of victory for the winner of the state in the last three presidential elections.

In North Carolina, another state with a close U.S. Senate race in 2026, Democrats voting by mail outnumbered Republicans by about eight percentage points in 2024, though mail ballots accounted for only about 5% of all votes, according to the data.

In a Friday statement to States Newsroom, Fair Fight Action CEO Lauren Groh-Wargo blamed Trump for undermining trust in vote-by-mail and encouraged voters to view mail voting as a viable method.

“Trump is a desperate loser who has spent years lying to his supporters about mail voting ‘fraud’ – as a result many stopped using a method they once trusted,” she said. “Voting by mail is secure, convenient, and accessible. Whether voting by mail, early, or on Election Day, make your plan to vote now and see it through.”

In a statement, White House spokeswoman Lauren Bis portrayed the rule on mail ballots as a “commonsense” election security measure.

“If securing America’s elections – through commonsense methods like voter ID and proof of citizenship – would make it harder for Democrats to win elections, perhaps they should reconsider the methods they’re using to ‘win,’” Bis wrote.

The Fair Fight analysis shows the partisan gap narrows in states with more mail-in voting.

In Arizona, where 83% of voters cast mail ballots in 2024, Republicans held a 5-point margin in mail voting, roughly the same as Trump’s 5.5-point victory in the state. And in Nevada, where 44% of ballots were cast by mail, the mail-in vote was almost evenly split among Democrat, Republican and “other” voters.

Mail voting history

Until 2020, mail voting enjoyed broad bipartisan support.

An April 2020 study published by Stanford University’s Institute for Economic Policy Research found that in the six Western states — Oregon, Washington, Colorado, Hawaii, Utah and California — that had started implementing a system of mailing ballots to every registered voter, the policy did not help either party while modestly boosting turnout.

“Vote-by-mail does not have meaningful partisan effects on election outcomes,” the authors wrote.

But as states ramped up mail voting in the 2020 election as a response to the COVID-19 pandemic, the issue turned more partisan, with Democrats more likely to stay away from in-person voting. 

Trump, then running for reelection, cast unfounded doubts on vote-by-mail’s integrity and warned of dire effects for Republicans.

“MAIL-IN VOTING WILL LEAD TO MASSIVE FRAUD AND ABUSE,” he tweeted in May 2020. “IT WILL ALSO LEAD TO THE END OF OUR GREAT REPUBLICAN PARTY. WE CAN NEVER LET THIS TRAGEDY BEFALL OUR NATION.”

After several cycles of roughly equal rates of mail voting, Democratic mail voters nearly doubled Republicans, 60% to 32%, in 2020. The gap narrowed in 2024, with Democratic voters outpacing Republicans 37% to 24%.

Trump’s claims

While the Postal Service is now arguing in court its rule based on Trump’s March 31 executive order is not an election regulation but only includes “modest” technical specifications for mail, other statements by Trump show the purpose is directly tied to election administration. 

Trump’s order justified new regulations on mail ballots to maintain “public confidence in election outcomes” and “enhance election integrity.”

He previewed the effort in an August 2025 social media post saying he would “lead a movement to get rid of MAIL-IN BALLOTS” that again made the issue explicitly about partisan advantage.

“WE WILL BEGIN THIS EFFORT, WHICH WILL BE STRONGLY OPPOSED BY THE DEMOCRATS BECAUSE THEY CHEAT AT LEVELS NEVER SEEN BEFORE, by signing an EXECUTIVE ORDER to help bring HONESTY to the 2026 Midterm Elections,” he wrote. “Democrats are virtually Unelectable without using this completely disproven Mail-In SCAM. ELECTIONS CAN NEVER BE HONEST WITH MAIL IN BALLOTS/VOTING.”

The U.S. Supreme Court is expected to rule soon on whether the rule can be in effect for this year’s midterms.

The hotly contested U.S. Postal Service rule restricting mail-in voting usurps Congress’ authority, as well as states’ power to administer elections, more than 250 current and former members of Congress said in a filing to the U.S. Supreme Court on Tuesday.

All 47 members of the U.S. Senate Democratic Caucus, 199 current House Democrats and 15 former House Republicans signed the friend-of-the-court brief opposing President Donald Trump’s policy to add several requirements to mail ballots. 

The U.S. Constitution “is unambiguous” in empowering states to run elections, while Congress can enact laws to oversee elections generally, they argued.

“Congress has passed several laws regulating federal elections—though it has always done so surgically, deliberately leaving the States with considerable room to maneuver,” they wrote.

The executive branch has no role, they said. 

The Trump administration has argued the rule, published last month, requires only “modest” technical specifications for mail ballots and that states transmit lists of eligible voters to receive the ballots. The rule is a targeted measure affecting mail delivery, not elections, the administration says.

But the lawmakers say that argument fails. 

The agency cannot take action related to elections without a congressional directive, they wrote. Congress never wrote a law asking for the requirements included in the USPS rule, they said. 

Executive order

In this case, Trump spurred the Postal Service to write the rule in a March executive order, based on the unsubstantiated premise that vote-by-mail is vulnerable to fraud. 

That shows the rule is meant to address Trump’s concerns about election administration, not mail specifications, the lawmakers said.

“The integrity of our constitutional system depends on each branch keeping to its assigned role,” they wrote. “The Framers set up a two-part system that gave States default authority to regulate federal elections subject to Congress’s authority to override the States. The Framers did not provide the President with any authority to interfere in that system, nor has Congress imbued the Executive Branch with any such authority by statute.”

Spokespeople for the White House, USPS and the Department of Justice, which is representing the Trump administration in the case, did not immediately return messages seeking comment Tuesday.

In a separate brief, the legal advocacy group the Society for the Rule of Law made a similar argument, saying the federal postal law the administration has cited provides only broad language that does not empower the agency to regulate election mail.

“The non-election, boilerplate … provisions on which Applicants rely are not a secret, alternative way for the USPS to bar ballot mail, conditionally or otherwise, on the eve of election day,” the group wrote. “Under the federalism presumption and the major question doctrine, the USPS needed a clear statement of statutory authority.”

Rushed delivery

The rule would require technical elements such as unique barcodes on ballot envelopes. Elections experts say those requirements are unworkable in time for the fall’s midterm elections because states have already designed, printed and — in some cases — begun sending ballots.

The rule would also require states to send to the federal government lists of eligible voters, which would be checked against a Department of Homeland Security database to verify citizenship. 

The rule bans the Postal Service from delivering ballots to registered voters who are not verified through that method.

The online portal that the rule says states should use for this process has still, less than two months until Election Day, not been introduced to states. A whistleblower last week reported the rushed development has led to myriad problems with the tool, which could result in legitimate ballots being rejected.

Opponents, including more than 20 Democratic state officials and voting rights groups that sued to challenge the rule, say it would risk disenfranchisement for the millions of voters, including Trump, who vote by mail.

High court ruling pending

The rule has been the subject of rapidfire legal fighting over the past several weeks, and the Supreme Court is now weighing whether to overturn a Massachusetts federal judge’s order pausing the rule while litigation continues, after the Trump administration filed an appeal over the weekend.

Justice Ketanji Brown Jackson on Sunday asked the states and voting rights groups challenging the rule to file their response to the application by Wednesday at 4 p.m. Eastern.

That district court injunction from Judge Indira Talwani, who was appointed by President Barack Obama, held that the rule was likely unconstitutional and unlawful for reasons the members of Congress articulated Tuesday: The Constitution grants states and Congress the power to oversee elections and states would be harmed if they are forced to comply with the regulation before courts can determine its legality.