Hillary Clinton speculated that "sabotage" of the United States Postal Service (USPS) could become the "Trump strategy" in aiding his reelection victory in November.

President Trump has repeatedly railed against mail-in voting, warning of voter fraud and delayed  results for the November 3 election against Joe Biden, although he reversed himself on Tuesday with his tweet endorsing mail-in voting for Florida residents.

On Tuesday, Clinton shared a Philadelphia Inquirer article -- which details residents' frustrations over mail delays and USPS staffing cuts -- and warned that the problems in Philadelphia could  become the entire country's problem under "Republican" watch. 

"I fear Republican sabotage of the USPS, including slowing mail delivery, is a Trump strategy to make voting by mail more difficult this fall," Clinton tweeted. "Request your ballots and return them as early as you can."

"Neighborhoods across the Philadelphia region are experiencing significant delays in receiving their mail, with some residents going upwards of three weeks without packages and letters, leaving them without medication, paychecks, and bills," the Inquirer reported on Monday, noting that the postal agency has undergone a round of cuts that eliminate overtime and slash work hours.

Local union leaders in Philadelphia allege mail is "piling up in offices, unscanned and unsorted" and that mail carriers are becoming "overwhelmed."

Critics of the defeated 2016 Democratic candidate claim her warning inadvertently proves that "vote fraud" is a risk with mail-in voting.

"You might be right. Best to just not do mail-in voting at all," Red State senior editor Brandon Morse told Clinton.

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"This is silly, tin-foil hat nonsense, but Clinton actually makes a very good point here (accidentally) that mail-in voting allows the executive branch of the federal government to handle ballots en masse for the election of the executive. One more reason it's a terrible idea," Daily Caller opinion contributor Eddie Zipperer tweeted.

Former Bush White House press secretary and Fox News contributor Ari Fleischer responded to Clinton on Twitter by highlighting a 2017 report from the Office of Special Counsel that alleged USPS workers violated federal law by letting employees do union-funded work for Hillary Clinton's campaign and other Democratic candidates while on leave from the agency.

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The OSC determined the USPS "engaged in systemic violations" of the Hatch Act, a federal law that limits certain political activities of federal employees. While employees are allowed to do some political work on leave, the report said the Postal Service showed a "bias" favoring the union's 2016 campaign operation.

According to the report, the work in various 2016 battleground states involved a total of 97 employees who took time off -- out of 600,000 USPS employees across the country.

“The Labor 2016 program sought to ‘elect Hillary Clinton and pro-worker candidates across the country,’” the report said, citing campaign work like door-to-door canvassing, phone banks and other get-out-the-vote efforts.

Fox News' Brooke Singman contributed to this report.