Another Sunday, another Trump Twitter war.

This time, President Trump, who is spending the day at his golf course in Virginia, took aim at retiring Republican Sen. Bob Corker of Tennessee.

And Corker fired back.

"It's a shame the White House has become an adult day care center," Corker wrote. "Someone obviously missed their shift this morning."

Later Sunday in a New York Times interview, Corker said Trump was treating the presidency like a reality show, and could set the nation "on the path to World War III."

In what has been widely perceived as an effort to save face, Trump claimed that Corker had "begged" the president to endorse him for re-election, but that Trump had turned him down. According to the president, that refusal is what ultimately led to the high-ranking senator's September announcement that he would not seek another term.

"Senator Bob Corker 'begged' me to endorse him for re-election in Tennessee. I said 'NO' and he dropped out (said he could not win without my endorsement). He also wanted to be Secretary of State, I said 'NO THANKS.' He is also largely responsible for the horrendous Iran Deal!"

Trump ended the trash-talking with this: "Hence, I would fully expect Corker to be a negative voice and stand in the way of our great agenda. Didn't have the guts to run!"

Corker, who is chairman of the Senate Committee on Foreign Relations, has been increasingly critical of the president in recent weeks, publicly airing his frustration with the dysfunction within the White House.

On Wednesday, he said, "I think Secretary Tillerson, (Defense) Secretary (Jim) Mattis and Chief of Staff (John) Kelly are those people that help separate our country from chaos."

And at a marathon Senate Budget Committee hearing this week, Corker expressed a deep disdain for the political theater of the job. "I have difficulty putting that much energy into discussing this budget document because this is some of the most meaningless work that we do here," Corker said with a sigh. "It has nothing to do with the chairman or the committee. It's a waste of time."

Shortly after Trump's Sunday morning tweets, Corker's chief of staff, Todd Womack, rebutted the president's claims, The Washington Post reports. Womack says that it was Trump asking for a favor.

The article states: "Trump called Corker early last week and asked him to reconsider his decision not to seek reelection, according to Womack. He said the president also reaffirmed that he would have endorsed Corker had he decided to run again — which, Womack added, was not the first time that Trump had extended such an offer of support."

Trump's latest feud with Corker comes at an inopportune time for Republicans trying to pass tax legislation. As NPR's Susan Davis reported, Corker could be a bigger threat to the Republican tax bill than the party realizes.

Just like on health care, Republicans can only lose two votes and still pass a tax bill if no Democrats or independents support it. That is why securing Corker's vote is critical.

But Corker has repeatedly said he views the deficit as the biggest threat to the nation.

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