The Senate’s top Democrat late Sunday asked the U.S. Postal Service’s governing board to turn over communication with the White House about the appointment of new Postmaster General Louis DeJoy, a sign that Democrats plan to press the Trump administration on its plans to consolidate control of the nation’s mail service.

Minority Leader Charles E. Schumer (D-N.Y.) wrote to Postal Service board of governors chairman Robert M. Duncan questioning whether DeJoy, a seasoned businessman and top fundraiser for President Trump who took office Monday, was “selected for reasons of politics or patronage” and how he’ll distance himself from the GOP and his vast financial portfolio.

The letter is the latest salvo in a growing political battle over the future of the USPS. As the Trump administration has sought to leverage the agency’s deteriorating finances to exert more control over its operations, congressional Democrats have pushed back to keep the USPS independent. DeJoy is an unusual selection as postmaster general because of his business and political ties — he ran a former Postal Service contractor that processed mail and maintained postal infrastructure — but it remains to be seen how he’ll run the agency.

Schumer requested correspondence between members of the postal board of governors and representatives of the Trump administration, notes from interviews with job candidates, contracts with the two search firms retained by the governors, and documentation on DeJoy’s stance on key issues facing the agency.

Schumer also sought a guarantee that DeJoy would resign as finance chair for the Republican National Convention and rid his extensive portfolio of any holding that conflicts with his new role.

“His financial interests in companies that have business ties with the Postal Service, as well as his extensive campaign fundraising efforts, also raise concerns regarding whether and how legal prohibitions on his ethical conflicts of interest and partisan political activity as a federal employee will be addressed,” Schumer wrote to Duncan, according to a copy of the letter obtained by The Washington Post.

DeJoy spokesman Monty Hagler declined to comment on Schumer’s letter, but told The Post that DeJoy resigned his position with the RNC effective Friday and “will comply with any financial divestitures that are required.”

DeJoy and his wife, Aldona Wos, the ambassador-nominee to Canada, have between $30.1 million and $75.3 million in assets in USPS competitors or contractors, according to Wos’s financial disclosure paperwork filed with the Office of Government Ethics. Postal Service mail processing contractor XPO Logistics — which acquired DeJoy’s company New Breed Logistics in 2014 — represents the vast majority of those holdings. Their combined stake in competitors UPS and trucking company J.B. Hunt is roughly $265,000.

Postal Service spokeswoman Kim Frum wrote in an email, before Schumer’s letter was sent, that the postmaster general is required to divest only from assets that present a conflict of interest so central to the agency’s operations that the postmaster general cannot recuse himself.

The North Carolina businessman and major Republican fundraiser succeeds Megan Brennan, whose 34-year career spanned from letter carrier to the agency’s first female leader. But the transition comes as the coronavirus pandemic has slashed revenue, and the Trump administration, led by Treasury Secretary Steven Mnuchin, is attempting to pull the independent agency into its sphere of influence.

Mnuchin has sought to leverage a $10 billion emergency loan to extract concessions from the Postal Service’s governing board, including the ability to approve the hiring of Brennan’s successor, according to several people familiar with negotiations. Board of governors vice chairman David Williams resigned over Mnuchin’s interference, frustrated that board members had capitulated to Treasury’s loan conditions, according to four people familiar with Williams’s thinking who spoke on the condition of anonymity because they’re not permitted to discuss ongoing negotiations.

Trump has called the Postal Service “a joke” and said he would not support a financial lifeline unless the agency quadrupled package prices, a move that experts say would devastate its finances by pricing out major package shippers and forcing them to enlarge their own distribution networks. To that end, the USPS last month launched a review of its package prices.

Into that fray steps DeJoy, one of the richest people in North Carolina, according to Business North Carolina magazine. He has donated more than $2 million to the Trump campaign and Republican causes since 2016, according to the Federal Election Commission, including $210,600 to the Trump Victory PAC on Feb. 19.

He hosted a fundraiser for the president and Republican National Committee in 2017 at his home in Greensboro, N.C., where plates started at $35,000 per couple, according to the Raleigh News & Observer.

He was in charge of fundraising for the Republican National Convention in Charlotte before it was moved last week to Jacksonville, Fla. His wife, Wos, is Trump’s ambassador-nominee to Canada and vice chair of the President’s Commission on White House Fellowships. Duncan, the chair of the USPS governing board, also chairs the fellowship commission and is a former RNC chairman.

Democrats have criticized DeJoy’s appointment as patronage, harking back to generations past when presidents doled out post office positions as political favors, and contend that he won’t preserve the agency’s independence.

“His only qualification is that he will do whatever Trump wants,” Rep. Peter A. DeFazio (D-Ore.) told The Post when DeJoy’s appointment was announced in May.

Conservatives have hailed DeJoy’s appointment as an injection of private-sector savvy into one of the government’s largest bureaucracies — one that is still intended to run like a business.

“He’s the most qualified person for that job outside of Fred Smith from FedEx. I’d only counter with Ben Franklin,” said former North Carolina Gov. Pat McCrory (R), alluding to FedEx’s chief executive and the nation’s first postmaster general.

DeJoy is the first postmaster general in decades to come from outside the Postal Service. His logistics background, conservatives say, will be key to navigating the complicated position the USPS serves as both competition to such shipping powers as UPS, FedEx and Amazon and the “last-mile” courier for those companies.

(Amazon founder and chief executive Jeff Bezos owns The Post.)

Even as volumes of first-class and marketing mail, the Postal Service’s most profitable items, have sharply declined during the pandemic, the agency’s finances have been propped up by package deliveries, which surged 38 percent in April compared to the same month in 2019.

Jeff Stein contributed to this report.