Reactions were swift and widespread on Wednesday to a Washington Post op-ed penned by Mitt Romney, in which the incoming senator from Utah described how President Donald Trump has not “risen to the mantle of the office.”

In an early morning tweet, Trump suggested that Romney should be a team player, while referencing Romney’s unsuccessful presidential campaigns.

“Would much prefer that Mitt focus on Border Security and so many other things where he can be helpful,” Trump wrote. “I won big, and he didn’t. He should be happy for all Republicans.”

At the White House on Wednesday, Trump reiterated his suggestion that Romney be more of a “team player.” Trump also remarked that he personally had great popularity in Utah, and said Romney would have been elected president if he had fought Barrack Obama as hard as he fights the current administration.

Polling has shown Trump’s approval rating in Utah to be near — and sometimes below — 50 percent, which is extraordinarily low for a Republican president in the majority-conservative Beehive State. And a September poll by Morning Consult found Utah to have the sharpest decline in approval ratings for Trump during 2018.

Romney’s op-ed was also rebuked by Ronna McDaniel, chairwoman of the Republican National Committee and Romney’s niece. McDaniel wrote in a tweet Wednesday that her uncle’s “attack” played into the hands of Democrats and the media.

“For an incoming Republican freshman senator to attack [President Trump] as their first act feeds into what the Democrats and media want and is disappointing and unproductive,” McDaniel wrote.

Romney defended his criticisms on CNN Wednesday, telling Jake Tapper that he has voiced concerns in previous op-eds and essays and that he felt compelled to clarify his position toward the administration after the firing of Defense Secretary James Mattis, the seemingly abrupt decision to withdraw U.S. troops from Syria, and his impending swearing-in to the U.S. Senate on Thursday.

“I think it’s important as I begin this new job to make it very clear where I stand,” Romney said.

After Tapper asked what specific actions by Trump had bothered Romney, the Sen.-elect cited Trump’s ambivalent response to the protests in Charlottesville, Va., his support for Roy Moore’s Alabama Senate campaign and his ongoing attacks on members of the media.

“I’ve laid out, time and again, places where I disagree with the president.”

Romney reiterated that he does not intend to mount another campaign for the presidency and said it’s too early to know whether he will endorse Trump’s re-election bid in 2020. Romney also said he does not regret accepting Trump’s endorsement last year.

“He was endorsing me,” Romney said. “I wasn’t endorsing him.”

Former FBI Director James Comey came to Romney’s defense, tweeting “Looks like the Republican tent is too small to fit integrity.”

While political watchers had a mixed response to Romney’s op-ed, with many remarking that his criticisms of the president were notable but that their impact is unclear. Ezra Klein, founder of Vox, said the op-ed is a “real risk from a usually risk-averse politician.” Nate Silver, founder of the website FiveThirtyEight, said Romney’s popularity in Utah makes him “untouchable” and free to speak out in ways that other Republicans are not. And Paul Krugman, a columnist for The New York Times, said that Romney had taken “the easy way out.”

Brad Parscale, Trump’s 2020 campaign manager, wrote that Romney lacked the ability to save the nation, and that Trump has saved it. He also commended Trump for his courage.

“Jealousy is a drink best served warm and Romney just proved it,” Parscale wrote.

But in a series of tweets, conservative political analyst Bill Kristol described Romney as the leader of the Republican resistance to Trump, and that his op-ed is indicative that Trump’s dominance over the Republican Party can no longer be taken for granted.

“Romney’s op-ed is a shot across the bow,” Kristol wrote. “Some are disappointed because it’s not a full-on assault on the Trump battleship. But it’s a shot. And shots across the bow are often followed by real boarding parties.”

He also questioned whether Parscale’s phrasing of a drink served warm was meant as an “anti-Mormon dog whistle” referring to The Church of Jesus Christ of Latter-day Saint’s prohibitions against coffee and teas, which are described as “hot drinks” in the faith’s Word of Wisdom.