(CNN) — The US Postal Service warned almost all of the 50 states and Washington, DC, that voters could be at risk of not getting their ballots back to election offices in time to be counted because election rules are not compatible with the time needed for delivery and return of absentee ballots through the mail, according to letters released on Friday night.

The letters provide a stark reminder that the expansion of mail-in voting due to the pandemic is colliding with a slowdown in postal delivery because of controversial changes made by the new postmaster general.

Most states were informed in late July by the service’s general counsel that postal service analysis suggests local deadlines for requesting and returning ballots did not allow for enough time based on delivery estimates.

The letters varied based on state rules, with a few states deemed to having sufficient time built in, according to the postal service assessment. But in total, the letters portray a last-minute warning some votes could be at risk, leaving some states scrambling to consider whether they have the ability to even adjust rules in time for the election.

The letters predate President Donald Trump’s most recent attacks on mail-in voting, including on Thursday when he said he opposed giving billions in funding to the postal service because doing so would allow increased mail-in voting. The changes are a result of previously planned cost-cutting measures, put in place partly as a reaction to the President’s extensive criticism of the US Postal Service as a money loser that does not charge enough for its services, combined with the coronavirus pandemic. Union officials have been warning that newly implemented measures would affect mail-in voting in November.

The popularity of voting by mail has exploded during the pandemic and it’s expected that Democratic voters plan to take advantage of expanded mail-in voting access more than Republicans.

News of the letters comes a little less than two weeks after the US Postal Service definitively said in a statement that it had the capacity to handle the added volume of mail-in voting anticipated in November.

READ: Letter from US Postal Service warns North Carolina it may not be able to deliver ballots on time

“Certain deadlines concerning mail-in ballots, particularly with respect to new residents who register to vote shortly before Election Day, appear to be incongruous with the Postal Service’s delivery standards,” USPS General Counsel Thomas Marshall wrote to California Secretary of State Alex Padilla. “This mismatch creates a significant risk that some ballots will not be returned by mail in time to be counted under your laws as we understand them.”

Letters detail timing break down

The letters list standard mail delivery times and prices for first class and marketing mail, the two types of mail USPS sends. Many states use the nonprofit marketing mail rate to send election mail, including absentee and mail-in ballots and ballot applications to voters.

The letters state that election mail must be sent from voters by first class mail, which is more expensive than the nonprofit marketing rate.

“State or local election officials may generally use either First-Class Mail or Marketing Mail to mail blank ballots to voters,” the letters state.

First class mail takes between two and five days to be received, while marketing mail takes between three and 10 days to be received, according to USPS. That, according to Pennsylvania’s secretary of commonwealth, is a longer a delivery time than what was factored in for the primaries in June, according to a filing in a related court case.

The slower delivery is, according to the court filing, a likely outcome of recent changes put in place by the post office that have been criticized for putting at risk the ability to conduct vote by mail across the country. As a result, Pennsylvania said it is willing to extend its deadline to receive ballots to up to three days after the election, provided they are mailed by Election Day.

USPS said the letters were intended to advise “election officials to be mindful of the potential inconsistencies between the Postal Service’s delivery standards, which have been in place for a number of years and have not changed, and the provisions of state law,” in a statement.

“During every election cycle, the Postal Service conducts regular outreach with state and local election officials regarding our mailing requirements, delivery standards and best practices for enabling voting by mail,” a USPS spokesperson said in a statement. “The Postal Service is well prepared and has ample capacity to deliver America’s election mail. However, the increases in volume and the effect of when volumes were mailed in the primary elections presented a need to ensure the Postal Service’s recommendations were reemphasized to elections officials.”

Secretaries of state implementing changes already

Both Michigan and Ohio’s secretaries of state offices said the letters reflect changes the states were already implementing to ensure that mail-in and absentee ballots would be mailed and received in time to be counted in the election.

Jon Keeling, spokesman for the Ohio Secretary of State, said the letter “reinforces reforms we’ve been working on since the primaries,” which include the design of the mail-in ballots so they stand out among other pieces of mail.

Michigan Secretary of State spokeswoman Tracy Wimmer said the letter “reiterates the importance of a number of things we are already doing,” like “working with USPS officials in Michigan to ensure that election mailings are prioritized in their system.”

Washington Secretary of State Kim Wyman was the first secretary to publicize that she had received the USPS letter.

Wyman was initially concerned when she received the letter, because Washington has historically sent mail-in ballots to every registered voter by first class mail at a nonprofit bulk mail price. She was concerned the letter indicated that if they sent their election mail at the nonprofit rate, they would have longer delivery times.

Wyman clarified with USPS officials in a call earlier this week that the state would still receive the nonprofit marketing bulk rate but get first class mail service when sending ballots to voters.

“I was certainly concerned that this was maybe some sort of messaging to let us know that if we did our mailing at a nonprofit low rate that we would have very long delivery times,” Wyman told CNN in a phone interview. “They chose their words carefully … they basically said, yeah, the mail delivery times would be what we’re used to.”

If Wyman had to change from paying the nonprofit bulk rate to paying the first class rate, it would have cost her $2.64 million to send 4.8 million ballots, as opposed to the $432,000 it will cost her to send the ballots at nine cents apiece via the nonprofit bulk rate.

As a state that has sent ballots to every registered voter before, Wyman and her office have a close relationship with their USPS counterparts. Wyman said she worries for states that are new to mail-in voting options who don’t have as strong relationships already established with the post office.

Wyman said she had a call “every day with the postal service” leading up to Washington’s primary. “It’s kind of just our relationship that we have with the postal service,” she said.

Top Democrats press for answers

News of the letters also comes as top congressional Democrats, including House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer, are pushing Postmaster General Louis DeJoy to answer what they call “grave questions about sweeping changes” he is instituting at hundreds of postal facilities.

In a 10-page letter sent Friday to DeJoy, the Democrats charge these changes are slowing the mail delivery and “therefore jeopardize the integrity of the election.”

“Rather than strongly advocating for the Postal Service’s request for emergency funding, it appears that you are now using funding shortfalls—which are being aggravated by the President himself—to justify sweeping operational changes that experts warn could degrade delivery standards, slow the mail, jeopardize crucial deliveries such as prescription medicines and essential goods, and potentially impair the rights of eligible Americans to cast their votes through the mail in the upcoming November elections,” the Democrats wrote.

The Postal Service has asked for $25 billion to help with budget shortfalls. That money is part of the negotiations between the White House and Democrats over a new Covid-19 stimulus bill.

Democrats also released two letters from Marshall, the USPS general counsel, to congressional leaders.

“We are currently unable to balance our costs with available funding sources to fulfill both our universal service mission and other legal obligations,” Marshall said in one of the letters. It outlined a number of operational changes the postal service is looking to implement.

In the second letter, Marshall said, “The Postal Service remains fully committed to fulfilling our role in the electoral process by doing everything we can to handle and deliver Election Mail, including ballots, in a timely manner consistent with our operational standards.”

The Democrats are asking for more details and documents about specific changes being proposed, the reason and the potential impact and asked for responses within a week.

According to the Democrats, DeJoy wrote a separate letter Friday to Pelosi and Schumer saying: “I also recognize that there have been unintended consequences related to these efforts that have impacted overall service levels.”

He added in that letter: “the Postal Service is working feverishly to address service problems.”

This story has been updated with additional comment from USPS, secretaries of state offices and top congressional Democrats.

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