Trump, responding to the piece, tweeted that Romney, a former GOP presidential candidate, should be “happy for all Republicans” and took a dig at outgoing Sen. Jeff Flake (R-Ariz.), who frequently criticizes the president but largely votes in favor of his policies.
“Here we go with Mitt Romney,” Trump tweeted Wednesday. “Question will be, is he a Flake? I hope not.”
He continued: “Would much prefer that Mitt focus on Border Security and so many other things where he can be helpful. I won big, and he didn’t. He should be happy for all Republicans. Be a TEAM player & WIN!”
Despite Trump’s “won big” claim, the president secured a smaller percentage of the national vote in the 2016 election than Romney did in the 2012 election.
Romney, who lost to President Barack Obama, won 47.2 percent of the national vote, compared with Trump’s 46.1 percent of the national vote in 2016. Romney easily won his Senate race in November, defeating Democrat Jenny Wilson with 62.6 percent of the votes.
Romney argued in his op-ed that the Trump administration has caused “dismay around the world” and that the president “has not risen to the mantle of the office.”
“It is well known that Donald Trump was not my choice for the Republican presidential nomination,” Romney wrote. “After he became the nominee, I hoped his campaign would refrain from resentment and name-calling. It did not.”
Ronna McDaniel, chairwoman of the Republican National Committee and Romney’s niece, blasted her uncle’s editorial as “disappointing and unproductive.”
“For an incoming freshman senator to attack [Trump] as their first act feeds into what the Democrats and media want and is disappointing and unproductive,” McDaniel tweeted.
Brad Parscale, Trump’s 2020 presidential campaign manager, defended the president against Romney’s criticism on Tuesday.
Romney “lacked the ability to save this nation,” Parscale tweeted. “Jealously is a drink best served warm and Romney just proved it.”
Romney will be sworn in as a junior senator in Utah on Thursday, replacing Orrin Hatch, the longest-serving Republican senator in U.S. history.
Romney has vacillated in his support of the president, but vowed in his op-ed to stand up against Trump during his Senate tenure.
“I do not intend to comment on every tweet or fault,” he wrote. “But I will speak out against significant statements or actions that are divisive, racist, sexist, anti-immigrant, dishonest or destructive to democratic institutions.”
This article has been updated to include comments by Parscale and McDaniel.
This article originally appeared on HuffPost.