Sen. Bob Corker has been on a roll attacking the president, and he kept it up Tuesday morning — which should make for a pretty awkward lunch when the two meet with Senate Republicans to discuss tax reform later in the day.

The Tennessee senator appeared on NBC’s “Today” show, saying he expects the lunch to be a mere photo op. “Hopefully the White House will step aside” and leave the process to Congress, he said.

The two have been feuding since before Trump took office, but the president’s tax plan, which calls for slashing taxes on individuals and corporations, turned up the heat. Corker, meanwhile, doesn’t want to support a bill that would increase the deficit.

Trump turned to Twitter to hit back at Corker, who he said “couldn’t get elected dogcatcher.” (Dogcatchers, it should be noted, are almost always appointed.)

After that, Corker sent out a tweet of his own: “Same untruths from an utterly untruthful president. #AlertTheDaycareStaff.”

Earlier this month, Corker tweeted that the White House has become an “adult day care center” for Trump. A deep dive on the status of the administration from the Washington Post revealed that aides and advisers reportedly “play rope-a-dope” with Trump and feign interest in his more unorthodox ideas in the hopes that he’ll forget about them and move on.

Later Tuesday morning, Corker also told CNN from Capitol Hill that Trump, who “has great difficulty with the truth,” is “debasing our country.” Asked whether he regrets supporting the president in the election, Corker said: “Let’s just put it this way: I would not do that again.”

Meanwhile, Trump fired off tweet after tweet aimed at Corker.

A rocky relationship

Trading barbs over taxes is just the latest spat in a drawn out public fight between Trump and “Liddle Bob Corker,” as Trump has christened the Tennessee senator. Throughout the election, Corker was slow to get behind his party’s candidate. Although he eventually said he “supported” Trump, he wouldn’t formally endorse.

During the early days of revelations about the Trump campaign’s questionable ties to Russia, Corker became one of the first prominent Republicans to speak out. He told reporters in May that the White House was in a “downward spiral” and months later, questioned whether Trump had shown the “stability” or “confidence” that “he needs to demonstrate in order to be successful.”

Since Corker announced that he wouldn’t seek reelection in September, he’s been especially ruthless in his attacks on the Trump administration. Corker told reporters on Capitol Hill that Chief of Staff John Kelly, Secretary of State Rex Tillerson, and Defense Secretary Jim Mattis “help separate our country from chaos.”

After weeks of Trump’s jingoistic threats over North Korea’s increasingly aggressive nuclear program, Corker also told the New York Times in October that the president was setting the U.S. “on a path to World War III.” It’s “like he’s doing ‘The Apprentice’ or something,” Corker added.