Postmaster General Louis DeJoy apologized Wednesday for “unacceptable” mail delays during the holiday season, an acknowledgement of troublingly low service delivery standards that plagued the beleaguered postal agency for much of 2020.

“During this peak season, we fell far short of meeting our service targets. Too many Americans were left waiting weeks for important deliveries of mail and packages,” DeJoy told lawmakers. “This is unacceptable, and I apologize to those customers who felt the impact of our delays.”

Tapped by President Donald Trump to lead the Postal Service last summer, DeJoy’s tumultuous tenure atop the mail agency has been marked by intense partisan scrutiny and a reform effort that slowed mail deliveries across the country.

While the Postal Service remains one of the nation’s most popular federal agencies, its leader became a political lightning rod ahead of the 2020 presidential election, when Democrats accused DeJoy – a longtime GOP donor – of deliberately delaying mail in a bid to undermine mail-in ballots, which were largely expected to support Democratic candidates. DeJoy and Postal Service vehemently denied those charges.

On Wednesday, during a hearing before the House Oversight Committee, lawmakers jousted over DeJoy’s performance. Rep. Jody Hice, R-Ga., decried Democrats’ criticism of DeJoy, calling them “conspiracy theories.”

Despite DeJoy’s deep unpopularity among Democrats, the incoming Biden administration has been unable to replace him. That power lies with the Postal Service’s governing board — whose six sitting members were all appointed by President Donald Trump as a result of a Republican-controlled Senate blocking a slate of President Barack Obama’s nominees.

The current slate of governors has expressed support for DeJoy and ignored repeated calls to remove him as postmaster general.

As a result, Democrats and influential mail union leaders have publicly pressured President Joe Biden to appoint new governors, who would need Senate approval.

Last week, more than 80 congressional Democrats urged Biden to nominate new governors “as expeditiously as possible” to “seriously consider whether the current Postmaster General is suitable to continue in his role.”