The day after Senate Republicans acquitted him in his impeachment trial, Donald Trump attended the National Prayer Breakfast, where the president took some not-so-subtle shots at Sen. Mitt Romney (R-Utah). As a rule, presidents don't use this event to settle scores and air grievances against perceived enemies, but Trump apparently couldn't help himself.

Soon after, as part of a bizarre hour-long event at the White House, he was even more aggressive toward a wide range of foes, including Romney. Referring to the Utah senator's vote to convict the president on one impeachment count, Trump said, "[T]he only one that voted against was a guy that can't stand the fact that he ran one of the worst campaigns in the history of the presidency."

For what it's worth, in Romney's 2012 bid for national office, he received 47% of the vote. Four years later, Trump received 46% of the vote. If Romney ran "one of the worst campaigns" ever, I'd love to hear why Trump couldn't quite match his vote total.

Regardless, the president's comments were emblematic of a larger truth: Trump has what Politico described as a "revenge list," and his shots at Romney were little more than an "opening salvo."

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Indeed, the Washington Post noted another name on the same list.

President Trump is preparing to push out a national security official who testified against him during the impeachment inquiry after he expressed deep anger on Thursday over the attempt to remove him from office because of his actions toward Ukraine. Lt. Col. Alexander Vindman -- a National Security Council aide who testified during House Democrats' impeachment hearings -- will be informed in the coming days, likely on Friday, by administration officials that he is being reassigned.... Trump is eager to make a symbol of the Army officer soon after the Senate acquitted him of the impeachment charges approved by House Democrats.

Remember, Vindman's serious misdeed, in the eyes of Trump World, is telling the truth and playing by the rules. The president appears eager to kick Vindman out of the White House, not only to punish the decorated war hero, but also to discourage others who may be tempted to act as honorably as Vindman did.

What's more, there's no reason to believe the "revenge list" is short. White House Press Secretary Stephanie Grisham declared during a Fox News interview yesterday, "People should be held accountable."

Last week, CBS News reported that key GOP senators had received stern warnings: those who cross the White House on impeachment, the report said, would find their head "on a pike." As part of the trial proceedings, House Intelligence Committee Chairman Adam Schiff (D-Calif.), the lead impeachment manager, mentioned the CBS News report, prompting Senate Republicans to feign apoplexy. How dare a Democrat, GOP senators said, suggest that their gracious and forgiving leader would stoop to retaliating against those who disappoint him.

Perhaps some of the Republicans who whined the loudest could take a moment to revisit their concerns now.

As we discussed the other day, Sen. Lamar Alexander (R-Tenn.) stood on the Senate floor in October 2009, and issued "a friendly suggestion" to President Obama and his White House: "Don't create an enemies list."

It was the right advice, directed at the wrong president.

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