GOP presidential front-runner Donald Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE is urging his supporters to stop watching Megyn Kelly’s show on Fox News.

“Everybody should boycott the @megynkelly show,” he tweeted Friday, referencing “The Kelly File." "Never worth watching. [It is] always a hit on Trump. She is sick [and] the most overrated person on TV.”

Everybody should boycott the @megynkelly show. Never worth watching. Always a hit on Trump! She is sick, & the most overrated person on tv. — Donald J. Trump (@realDonaldTrump) March 18, 2016

Fox News personality Geraldo Rivera took to Twitter to defend his colleague.

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“I love you man but basta,” he tweeted at the outspoken billionaire. "This obsession with @megynkelly is weird [and] unhelpful. She’s doing her job, you do yours."

@realDonaldTrump @megynkelly I love you man but basta. This obsession w @megynkelly is weird & unhelpful. She's doing her job, you do yours. — Geraldo Rivera (@GeraldoRivera) March 18, 2016

A spokesperson for Fox News fired back at Trump, saying he has a “sick obsession” with Kelly.

“Donald Trump’s vitriolic attacks against Megyn Kelly and his extreme, sick obsession with her is beneath the dignity of a presidential candidate who wants to occupy the highest office in the land.

"Megyn is an exemplary journalist and one of the leading anchors in America — we’re extremely proud of her phenomenal work and continue to fully support her throughout every day of Trump’s endless barrage of crude and sexist verbal assaults. As the mother of three young children, with a successful law career and the second highest rated show in cable news, it’s especially deplorable for her to be repeatedly abused just for doing her job.”

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Trump's call for a boycott is just the latest escalation in his feud with Kelly. The two sparred during the first GOP presidential debate in Cleveland on Aug. 6th. Kelly, a moderator, sharply questioned Trump over his past remarks towards women.

Trump was outraged by Kelly’s questioning, saying a day later that “she had blood coming out of her nose – out of her wherever.” He then skipped the a Fox News-hosted debate in Des Moines, objecting to Kelly’s role as a moderator.

Kelly on Wednesday hosted Sen. Ted Cruz Rafael (Ted) Edward CruzSenate Republicans face tough decision on replacing Ginsburg Cruz: Trump should nominate a Supreme Court justice next week Renewed focus on Trump's Supreme Court list after Ginsburg's death MORE (R-Texas), Trump's GOP presidential rival, on her show. She also tweeted a poll the following day showing that American women increasingly are viewing Trump unfavorably.

Trump has since repeatedly referred to Kelly as “crazy Megyn” on Twitter, accusing her of bias.

Critics have accused Trump of misogyny, citing his fight with Kelly.

One anti-Trump group released an ad Monday, highlighting past controversial remarks he's made about women.

“If you believe America deserves better, vote against Donald Trump,” the clip from Our Principles PAC said, after having women repeat Trump’s past insults including “bimbo” and “fat pig."

Updated at 7:37 p.m.