Republican Rep. Ryan CostelloRyan Anthony CostellloRep. Brendan Boyle decides against Pennsylvania Senate bid Pennsylvania's Democratic lt. governor files to run for Senate Bottom Line 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 McCainMeghan McCain to produce 'Don't Sweat the Small Stuff' Lifetime movie starring Heather Locklear An August ultimatum: No recess until redistricting reform is done Meghan McCain on Pelosi, McCarthy fight: 'I think they're all bad' 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 BidenJoe BidenCDC chief clarifies vaccine comments: 'There will be no nationwide mandate' Overnight Defense: First group of Afghan evacuees arrives in Virginia | Biden signs Capitol security funding bill, reimbursing Guard | Pentagon raises health protection level weeks after lowering it Biden urges local governments to stave off evictions 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 TrumpMeghan McCain: Democrats 'should give a little credit' to Trump for COVID-19 vaccine Trump testing czar warns lockdowns may be on table if people don't get vaccinated Overnight Health Care: CDC details Massachusetts outbreak that sparked mask update | White House says national vaccine mandate 'not under consideration at this time' 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."