CHARLESTON, W.Va. (AP) — A post-impeachment spat between President Donald Trump and U.S. Sen. Joe Manchin has sunk to name-calling and insults.

The moderate Democrat took to cable news Monday to hurl barbs at the president after a weekend of back-and-forth that ignited when Trump criticized Manchin for voting to impeach him from office.

“I expect every American, and myself, would like my president and our president to act like a responsible adult, and he’s not,” Manchin told CNN. “And I hope he does, for the sake of our country, I hope he does.”

The feud began Friday evening when Trump tweeted that he was “very surprised & disappointed” with Manchin’s impeachment votes and that no president has done more for West Virginia. In a subsequent tweet, Trump said Manchin was “just a puppet” for the Democratic leaders in the House and Senate.

“That’s all he is!” Trump tweeted.

The president’s comments were seen as a move to weaken the senator’s standing in West Virginia, where Trump won nearly 70% of the vote in the 2016 election.

On Saturday night, Manchin fired back via Twitter, saying “no Democrat has worked harder in a bipartisan way in the hopes that you would succeed.” He added that West Virginia residents “know exactly” who has worked day and night for the last five years to secure their health care and pensions, and “it wasn’t you.”

Trump then followed up on Sunday, tweeting “they are really mad at Senator Joe Munchkin in West Virginia. He couldn’t understand the Transcripts.”

In another interview Monday morning, this time with MSNBC, Manchin responded to Trump’s new nickname for him.

“Well, first of all, the munchkin — I’m taller than him, I think I’m a little bigger than he is, not heavier, he’s much heavier than me but I’m a little taller than him so I guess he’s got that a little bit off,” Manchin said.

Trump was acquitted by the Senate on Wednesday on charges that he abused his office after senators narrowly rejected Democratic demands to summon witnesses for the impeachment trial.

In announcing his decision on the impeachment vote Wednesday, Manchin said the evidence presented by House managers clearly supported the charges brought against the president.

“I take no pleasure in these votes, and am saddened this is the legacy we leave our children and grandchildren,” Manchin said. “I have always wanted this president, and every president, to succeed, but I deeply love our country and must do what I think is best for the nation.”

At least before the caustic bickering, Trump and Manchin appeared to have a warmer relationship than the president has with most other Democrats.

The senator noted in his interviews Monday that he’s one of the rare people on the other side of the political aisle willing to work with the president. He was also invited to the White House when the president presented former basketball player Bob Cousy with the Medal of Freedom and was present when Trump presented the Medal of Freedom to another former basketball great, West Virginia native Jerry West.

A spokeswoman for Manchin’s office on Monday said the senator hasn’t spoken with Trump since the president’s tweets on Friday.

Manchin was previously governor of West Virginia and is serving his second term as U.S. senator. He won the second term in 2018 after a tight race against a Trump-backed challenger.

The president has also taken aim at other lawmakers who voted to impeach him, including U.S. Sen. Doug Jones, an Alabama Democrat, as well as U.S. Sen. Mitt Romney, a Utah Republican.

During a meeting with the nation’s governors at the White House on Monday, Trump got a question from Utah’s governor and before answering the question, said: “How’s Mitt Romney? You can keep him. We don’t want him.”