WASHINGTON - A long-serving Republican appointee to the Federal Election Commission announced his resignation on Monday, leaving the polarized panel without a four-person quorum to conduct business for the first time in 11 years.

Matthew Petersen, who has sided with his GOP colleagues in favor of less regulation of the election process, will leave the FEC on Saturday. He did not specify a reason for his departure in his resignation letter to President Donald Trump.

“The work of a Commissioner is challenging because it involves taking actions that impact the free speech rights of the American people,” Petersen said in statement Monday. “For this reason, I take satisfaction in having fulfilled my obligation to safeguard First Amendment interests while faithfully administering and enforcing the federal campaign finance laws.”

Petersen served as FEC commissioner since President George W. Bush appointed him in 2008, well beyond his six-year tenure. After serving as chairman in 2010 and 2016, he almost left the panel when Trump nominated him to the federal judiciary in 2017.

But he withdrew from consideration after struggling to answer questions about legal procedure during his confirmation hearing before the Senate Judiciary Committee.

Without Petersen, the six-member panel is left with three commissioners - one Republican, one Democrat and one independent - who are all serving expired terms. The seats formerly held by Democratic appointee Ann Ravel and Republican appointee Lee Goodman have remained vacant for years.

Four votes are required to take official action, such as enforcing regulations, issuing advisory opinions or approving audit reports.

The lack of a quorum will further complicate the ability of the FEC - which has long been ideologically split - to monitor compliance with election law as the 2020 campaign is ramping up.

“It’s never a good time for the commission not to have a functioning body,” said Kenneth Gross, former FEC general counsel. “But we are approaching a federal election year and there may be additional matters that are coming up at this time.”

The deplenished panel puts pressure on Trump to fill the vacant positions and make good on his campaign promise to address what he called a “rigged” campaign finance system.

The White House did not respond to questions Monday about how it plans to address the empty FEC seats.

According to a senior GOP Senate aide, there are discussions about nominating a slate of six new appointees and remaking the panel entirely.

To do that, Senate Minority Leader Charles Schumer and Senate Democrats “must replace the two longtime Democratic holdovers,” said the aide, who requested anonymity to speaking freely about ongoing discussions. “A clean slate of members will go a long way toward fixing some of the perceived dysfunction at the commission.”

Schumer’s office did not immediately respond to a request for comment.

Since taking office, Trump has nominated one person to the FEC: Texas lawyer James “Trey” Trainor, who was tapped back in September 2017. The Senate is yet to hold a confirmation hearing for Trainor.

Trainor has been a staunch proponent of less regulation of money in politics. He has challenged the principle that the public benefits from the disclosure of political donors, arguing that voters could be distracted from the content of political messages if they focus on who is financing ads

Charles Spies, a Republican campaign finance lawyer, said he does not expect the inactive panel to dramatically change candidates’ financial conduct. He noted that there is a five-year statute of limitations for the FEC to take action, which means that any illicit activity would, in all likelihood, eventually come before a functioning panel.

“In my experience, candidates and organizations attempt to comply with the law, and if they have violations, it was not because of some Machiavellian calculation about how many commissioners would be on different sides of the issue,” he said. “It is normally an innocent mistake.”