Mitt Romney says Donald Trump ‘has not risen to the mantle of the office’

US President Donald Trump on Wednesday cautioned fellow Republican Mitt Romney to be a “team player” after the former presidential candidate and incoming US senator sharply criticised the president’s actions and questioned his character. In a Washington Post essay published late on Tuesday, Romney suggested the US leader had “caused dismay around the world” and said his presidency had “made a deep descent in December.”

“On balance, his conduct over the past two years ... is evidence that the president has not risen to the mantle of the office,” said Romney, who starts his new role representing Utah on Thursday. “The appointment of senior persons of lesser experience, the abandonment of allies who fight beside us, and the president’s thoughtless claim that America has long been a ‘sucker’ in world affairs all defined his presidency down,” he wrote.

The White House did not respond to a request for comment, but Trump fired back in a tweet on Wednesday taking aim at Romney’s failed 2012 White House bid.

“Here we go with Mitt Romney, but so fast! Question will be, is he a Flake? I hope not. 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!” Trump wrote on Twitter, appearing to reference outgoing US Senator Jeff Flake, one of the few Republican lawmakers who publicly spoke out against Trump, at the cost of drawing the president’s wrath.

It is unclear whether any other Republican lawmakers will feel emboldened to criticise Trump ahead of his presumed 2020 re-election bid or whether Trump will face any serious challengers for the Republican Party’s presidential nomination. Romney’s move to stake out a more independent position highlights divisions within the party, since Trump upended many conservatives’ long-held positions on foreign policy and deficits, among others.

Republican National Committee Chair Ronna McDaniel also criticized Romney on Twitter, calling his essay an “attack” on Trump that was “disappointing and unproductive.”