House Republicans on Thursday took aim at Speaker Nancy Pelosi over a reimposed mask mandate in the chamber.

During a news conference on the steps outside the Capitol, Minority Leader Kevin McCarthy questioned why the House was again required to mask up while face coverings were only recommended for the Senate.

“What's interesting, we stand out here in front of the Capitol by the chambers of the House,” McCarthy said, “but as you look across on the other steps is the Senate. I'm not quite sure where the CDC got it, but somewhere in the middle about that dome (in between), the science changes.”

While the Republicans directed their fury at Pelosi and suggested the decision was not based on science, the directive actually came from Dr. Brian Monahan, Congress’ attending physician. He made the decision shortly after the Centers for Disease Control and Prevention revised its guidance to recommend that fully vaccinated Americans wear masks indoors in parts of the U.S. where COVID-19 is surging.

Rep. Brad Wenstrup, R-Ohio, also argued there was no factual basis for the House’s mask policy. 

“We're being asked to follow CDC guidelines here, and the mask mandates being inflicted on the House of Representatives doesn't match the guidelines for D.C.,” he said during Thursday’s news conference.

While Washington does not meet the threshold of high or substantial COVID-19 risk, as defined by the CDC, Monahan explained in an email to lawmakers that a mask mandate in the House was warranted because the chamber represents “a collection of individuals traveling weekly from various risk areas (both high and low rates of disease transmission).”

Washington Mayor Muriel Bowser announced just hours after the GOP news conference that masks would be required again in public indoor spaces in the district regardless of someone’s vaccination status.

Monahan’s office has not responded to a request for comment about why the doctor ordered a mask mandate for the House but not the Senate. However, the Senate is a far smaller body, and a CNN survey found that all but four of its members have publicly confirmed they have been vaccinated. Meanwhile, nearly half of House Republicans are not sharing their vaccination status publicly, CNN reported, although McCarthy claimed the body was 85% vaccinated.

McCarthy and Pelosi have been trading barbs over the mask mandate in recent days. After McCarthy tweeted Tuesday night that the policy “is not a decision based on science, but a decision conjured up by liberal government officials who want to continue to live in a perpetual pandemic state,” Pelosi called the Republican leader a “moron.”

“We believe in science and we want a speaker that will take the time to understand the science instead of just calling people names,” McCarthy said Thursday.

Pelosi told reporters Wednesday that she is simply following the guidance of Congress' attending physician.

"There is no discussion about should we do it, should we not for one reason or another,” Pelosi said. “It’s the decision of the Capitol physician, who is following the guidance of the CDC about the masks.”

McCarthy took his criticism even further than Pelosi, attacking the CDC for changing its guidance on masks. He accused the public health agency of basing its decision on a study that has not been peer-reviewed about viral transmission in India among people who had received a vaccine that is not currently available in the United States.

CDC Director Dr. Rochelle Walensky has defended the change by saying there was new evidence that vaccinated Americans with “breakthrough” COVID-19 cases could spread the virus to others. 

The CDC has not responded to an inquiry Thursday asking if there was any truth to McCarthy’s allegation and where it received the data that prompted the change. 

“It punishes Americans who've already done everything they were asked to do,” McCarthy said of the CDC guidance. “They were told to be vaccinated, they wouldn't have to wear a mask.

“The CDC has become a political arm of the administration,” he added. “It wants to control every element of our life.”

The White House has continually stressed that President Joe Biden is not involved in public health guidance. 

The House’s previous mask rule was lifted June 11. Prior to then, several House Republicans criticized the policy, especially the longer it lasted. Three members were fined $500 for violating the rule, and at least seven others were issued warnings.

On Tuesday, even before the mandate was reinstated, the three lawmakers who were fined — Reps. Marjorie Taylor Greene of Georgia, Thomas Massie of Kentucky and Ralph Norman of South Carolina — announced they had filed a lawsuit accusing Pelosi of violating the Constitution by docking their pay. 

The House voted to impose fines for members who do not wear masks, and the House Ethics Committee upheld the fines that were levied. 

When asked during an appearance on Fox News on Thursday if he’ll comply with the reinstated mask mandate, Massie answered, “Hell no!”

“We'll take it all the way to the Supreme Court if we have to. She's a tyrant and a hypocrite,” he said, referring to Pelosi.

The mandate also prompted an angry confrontation Wednesday, as Rep. Maxine Waters, D-Calif., verbally assailed Rep. Burgess Owens, R-Utah, who exited the House chamber and walked past her without a face covering.

Conservatives also forced a vote to adjourn the chamber in protest to the mandate, which was defeated along mostly party lines.

“We have a crisis at our border, and we’re playing footsie with mask mandates in the people’s House,” railed Rep. Chip Roy, R-Texas, the motion’s sponsor. “The American people are fed up. They want to go back to life. They want to go back to business. They want to go back to school without their children being forced to wear masks.”

The Associated Press contributed to this report.