Sen. Angus King is raising concerns about the U.S. Postal Service’s declining quality of service and questioning its ability to handle the influx of mail expected around the November general election unless officials walk back recent management decisions intended to reduce the agency’s spending.

The Maine independent’s concerns were summarized in a letter he sent Thursday to fellow Sen. Gary Peters, D-Mich., the ranking member on the Senate’s Committee on Homeland Security and Governmental Affairs, which oversees Postal Service operations. In it, King cited recent comments from over 4,500 constituents, sources inside the Postal Service and the Press Herald’s reporting on the Portland post office’s intentional delay of mail.

The senator, a longtime advocate for the Postal Service, stressed in his letter that it is an essential service and should not be run like a for-profit business.

King said his constituents are concerned about the financial stability of the Postal Service and worried it may not be up to the task of handling the large number of mail-in ballots that are likely to flood post offices as the Nov. 3 general election approaches.

“Over 1,200 people have contacted my office since June 15 to encourage me and Congress to make sure mail-in voting is organized, funded, and ready for the election in three months,” King wrote.

Peters said Thursday he is launching an investigation into changes at the Postal Service that are causing delays in mail deliveries across the country just as big volume increases are expected for mail-in election voting, The Associated Press reported.

In an interview Thursday, King said his letter to Peters is just one of what he called “a variety of points of the compass to put pressure on the negotiators to do something serious about helping the post office.”

King said he hopes the letter will prompt Congress to finally repeal a mandate it imposed in 2006 that requires the Postal Service to prefund the anticipated cost of health care benefits for all its retirees for the next several decades, a move that has proved financially difficult. He also has been in contact with Senate Minority Leader Chuck Schumer, D-N.Y., who met with the new postmaster general, Louis DeJoy, on Tuesday.

King said that DeJoy’s strict ban on overtime pay and attempts to close rural post offices and cut the hours of postal workers address the symptoms, but not the problem.

“I think what we need to do is twofold,” King said. “We have to undo that (ban on overtime), and we should provide them the financial wherewithal to make such steps unnecessary. No business that I know of improves its bottom line by degrading service.”

If Congress is able to reach agreement on a coronavirus relief package, King said he is “cautiously optimistic” that it will include somewhere between $10 billion and $25 billion in relief funds for the Postal Service to help it through the current crisis.