Republican Rep. Ryan CostelloRyan Anthony CostellloDems eyeing smaller magic number for House majority House GOP starts summer break on a note of friction Overnight Energy: Proposed rule would roll back endangered species protections | House passes Interior, EPA spending | House votes to disavow carbon tax MORE (R-Pa.) on Friday called on the White House to fire special assistant Kelly Sadler over her derisive remarks about Sen. John McCainJohn Sidney McCainDem strategist: Trump thinks of McCain as 'he who should not be named' Omarosa book: Trump called Montenegro prime minister a ‘whiny punk b----’ The Hill's Morning Report — Trump’s GOP feuds dominate ahead of midterms MORE (R-Ariz.). 

"I think the White House should apologize and fire her. I think the remarks are disgusting. It's depressing, Craig, when you hear that kind of talk when you look at the service of Sen. McCain," Costello told CBS News host Craig Melvin.

"As a party, I think we need to do a better job of getting out in front of this stuff quickly, condemning it, and saying it has no place in our discourse," Costello added.

Echoing similar comments from former Vice President Joe BidenJoseph (Joe) Robinette BidenTech companies earn White House praise for committing to easier health data access Biden honors Heather Heyer: She is 'in every person who stands up to reject hatred and bigotry' Avenatti on 2020 campaign: 'The truth is my policy issue' MORE, Costello said mocking a dying senator represented a degradation in America's political discourse.

During a closed-door meeting on Thursday, The Hill reported, Sadler dismissed McCain's opposition to President TrumpDonald John TrumpDems make history, and other takeaways from Tuesday's primaries Pawlenty loses comeback bid in Minnesota Establishment-backed Vukmir wins Wisconsin GOP Senate primary MORE's CIA director pick, Gina Haspel, stating “It doesn’t matter, he’s dying anyway.”

Sources familiar with the matter told The Hill that they believed the comment was meant as a joke, though it did not go over well with White House communications staffers present at the meeting.

McCain, 81, was diagnosed last year with an aggressive form of brain cancer, which he is receiving treatment for at his home in Arizona.

The White House is facing mounting scrutiny over its refusal to acknowledge the incident, drawing criticism from lawmakers on both sides of the aisle and members of the media.

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During Friday's daily press briefing, White House press secretary Sarah Huckabee Sanders refused to address the matter, dodging questions about Sadler's comments. 

“I'm not going to validate a leak, one way or another, out of an internal staff meeting," Sanders said at the briefing. 

Sadler, reportedly, has since apologized to the senator's daughter, Meghan McCain, who has also called for Sadler to be fired.

Meghan McCain, who co-hosts "The View," said Friday she couldn't understand an environment in which an aide could make such a comment and then "could come to work the next day and still have a job."