President Trump finally chose a new Republican commissioner for a key panel of federal energy regulators. But he did so without naming a Democrat to go with him, setting off a potential battle with Senate Democrats over the future of renewable energy and gas pipeline projects across the country.

On Monday, the White House announced the president intends to nominate James Danly to be a commissioner on the Federal Energy Regulatory Commission. Danly, a Republican, currently serves as the panel’s general counsel and would fill a vacancy left by the death in January of former FERC chairman Kevin J. McIntyre. If confirmed by the Senate, Danly would serve until 2023.

But Trump’s White House broke with decades-old tradition by not nominating a Democrat along with Danly, provoking the ire of Senate Democrats who charge Trump with potentially tilting the balance of the normally bipartisan commission.

“The administration should not play politics with our national energy policy and instead follow tradition by formally nominating both a Republican and a Democrat as a pair to the Federal Energy Regulatory Commission,” Senate Minority Leader Charles E. Schumer (D-N.Y.) said in a statement Tuesday.

The five-member energy panel has a sweeping portfolio, regulating portions of the electricity grid, interstate oil transportation and natural gas pipelines. If Danly is confirmed without a Democrat, the panel would move forward on a number of key decisions in the coming months with three Republicans and only one Democrat.

FERC has two openings — one to be filled by a Republican, the other by a Democrat. Congress designed FERC to have no more than three members from the president’s own party.

“Having a full commission is more likely to get you towards nonpartisanship and independence, both of which have been hallmarks of FERC in the past. It’s not just lip service,” said John Moore, who focuses on electric grid issues at the Natural Resources Defense Council. “That gives industry, and everyone else, a lot more faith in power markets.”

The commission showed that independence when in early 2018 the Trump-appointed regulators unanimously rejected a plan from Energy Secretary Rick Perry to rescue struggling coal and nuclear plants.

The recent foot-dragging from the White House, which did not reply to a request for comment, was not for lack of effort on the part of Senate Democrats.

Earlier this year, Schumer and Sen. Joe Manchin III (W.Va.), the ranking Democrat on the Senate Energy and Natural Resources Committee, recommended that energy lawyer Allison Clements replace a Democratic commissioner, Cheryl LaFleur, who stepped down at the end of August.

The Senate under both Barack Obama in 2012 and George W. Bush in 2006 treated Republican and Democratic FERC nominations as a package. Trump did so once in 2017 when he sent the nominations of McIntyre, a Republican and Richard Glick, a Democrat, to the Senate simultaneously.

All FERC commissioners are required to be confirmed by the Senate. The White House could ultimately send Danly’s and Clements’s nominations to the chamber as a package.

“Putting up only one nominee in this situation is unique,” said Jeff Dennis, who worked at FERC for 11 years before becoming managing director and general counsel at Advanced Energy Economy, a clean-energy trade association. “It would tip the balance more severely at the commission than it is right now.”

Near the top of FERC’s chock-full agenda is a potential new rule to make government-supported renewable energy generation more expensive for 65 million people who get power from PJM Interconnection, a regional transmission system that covers all or parts of 13 states stretching from Illinois to New Jersey, as well as the District of Columbia.

Ten Senate Democrats, worried the new regulations from the GOP-controlled panel could undermine Democratic state policies designed to support clean energy, oppose the yet-to-be-finalized rule, calling it “federal overreach” in an Aug. 29 letter to FERC Chairman Neil Chatterjee.

Chatterjee, who joined FERC last year after working as an energy policy adviser to Senate Majority Leader Mitch McConnell (R-Ky.), is also eager to accelerate approvals of natural gas pipelines and export facilities.

But Glick, the lone remaining Democrat on the panel, has argued FERC has done a “poor job” taking into account the climate impacts of building more gas pipeline. Chatterjee has said considering how more natural gas infrastructure could speed up climate change is outside the purview of the commission.

So far, Sen. Lisa Murkowski (R-Alaska), the chairwoman of the Senate energy panel, through Danly’s nomination must pass, isn’t saying whether she would move forward with just the Republican nomination.

“I welcome the President’s decision to nominate a Republican commissioner and to fill a critical seat that has now been vacant for nine full months,” Murkowski said in a statement. “We will need to receive both a formal nomination and all associated paperwork before proceeding to a hearing, which has not been scheduled at this time.”