President Donald Trump Wednesday called on incoming Utah Sen. Mitt Romney to be "happy for all Republicans" and to be a "TEAM player" in response to a scathing column the one-time Republican presidential nominee penned for The Washington Post saying Trump had not "risen to the mantle" of the presidency.

"Here we go with Mitt Romney, but so fast!" Trump tweeted. "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's tweet followed a scathing attack on Romney by former Secret Service agent Dan Bongino on Fox News' "Fox and Friends," who called the incoming senator a "fraud" and a "phony" who has "absolutely decimated the Republican Party."

He compared him to outgoing Arizona Sen. Jeff Flake, who he said had to "pass the baton of GOP sellouts" but complained Romney couldn't wait to be sworn in to attack.

"He endorsed Romney, the president," said Bongino. "You want to talk about character, you big, phony, fraud, fake. You should have never taken that endorsement if this is how you felt."

Trump, meanwhile, has been "crystal clear" about his agenda from the start, but Romney wrote an opinion piece "flaying Trump for character issues."

"Maybe if Romney was a true conservative and not a phony we wouldn't have had to deal with two terms of Barack Obama," said Bongino.

He also speculated that Romney is either setting himself up to run against Trump in 2020 or to "back some swamp rat" to mount a campaign.