RALEIGH, N.C. (AP) — North Carolina Sen. Thom Tillis said on Friday he “fell short of my own standard” by failing to keep his face mask on in the White House crowd while listening to President Donald Trump accept the Republican nomination.

Tillis, who is in a tough reelection bid against Democrat Cal Cunningham, has been consistently talking up face coverings as a chief method to slow the spread of COVID-19. At dozens of virtual town hall meetings, he’s urged participants to wear them when near others.

Tillis’ campaign tweeted a picture of the first-term senator wearing a mask on the South Lawn of the White House on Thursday night before Trump’s speech. But other media outlets later showed images of the crowd during the speech. There sat Tillis within the tightly packed, largely unmasked crowd, also not wearing a mask.

“I’ve stressed the importance of mask wearing throughout this pandemic and have tried to lead by example on this issue, but last night I fell short of my own standard,” Tillis said in a statement released through his campaign.

Democrats jumped on the unforced error, accusing Tillis of being a hypocrite.

“When it comes time to choose between his political career and his principles, Tillis chose what’s best for himself,” state Democratic Party spokesperson Robert Howard said in a news release. “Sen. Tillis criticizing others while not following his own words is a perfect encapsulation of why North Carolinians don’t trust Tillis, and why he’ll be out of office this fall.”

Tillis, whose seat is one of a handful Democrats hope to pick up to take back the Senate in 2021, embraced mask wearing months ago when other Republicans, particularly Trump, dismissed the idea.

“I started wearing a mask the day the (White House) COVID task force said start wearing masks. I’ve worn one ever since,” Tillis told restaurant leaders at a small in-person campaign event Tuesday in Raleigh.

Tillis, the former state House speaker, also has admonished those people who don’t wear them, especially when they enter businesses.

“It’s also important to maintain distance,” he said at a conference call with constituents Thursday afternoon discussing state coronavirus guidelines. That means, he added, to “certainly not even linger for long periods of time around anyone, particularly people not wearing a mask.”

Tillis tried to spin his mistake into an attack on Cunningham, who has been shown to be leading in several polls and outraised Tillis during the two previous quarters.

He accused Cunningham of making excuses for things like raising taxes while a state senator in 2001 and said, unlike the Democrat, “I can accept responsibility for my actions.”