Sen. Bob Corker (R-Tenn.) accused President Trump of “debasing” the country with his “untruths,” “name-calling” and “attempted bullying,” escalating his criticism of the president and heightening their feud just as Trump arrived on Capitol Hill to meet with GOP senators on Tuesday about tax legislation.

“For young people to be watching, not only here in our country, but around the world, someone of this mentality as president of the United States is something that is I think debasing to our country,” said Corker, whom Trump soon attacked on Twitter.

“You would think he would aspire to be the president of the United States and act like a president of the United States. But that’s just not going to be the case, apparently,” Corker said.

Trump addressed Senate Republicans at their weekly policy luncheon just hours after his feud with Corker exploded on Twitter and cable news.

The gathering was billed as a chance for Trump to discuss the GOP’s effort to cut taxes, and Corker’s comments did not come up, according to two senators who attended the luncheon. Republican senators hoping for specific guidance on taxes and health care received an update instead on Trump’s accomplishments since taking office.

Senate Majority Leader Mitch McConnell R-Ky.) and President Trump arrive for the Republican Senate Policy Luncheon at the Capitol. (Chip Somodevilla/Getty Images)

“It wasn’t a whole lot about taxes,” said Sen. John Cornyn (R-Tex.), the second-ranking Republican. “It was about the record in the last nine months and the successes in terms of the regulatory environment, consumer confidence, the stock market, and also the need to get the work done.”

Cornyn said Trump did “sort of survey the group” on various potential nominees for Federal Reserve chairman. He would not say which potential candidate received the most support during the show of hands.

After the lunch meeting, Senate Majority Leader Mitch McConnell (R-Ky.) declined to address Trump’s feud with Corker or questions about Trump’s fitness for office.

“If there’s anything that unites Republicans, it’s tax reform,” McConnell said at a news conference. “We’re going to concentrate on what our agenda is and not any of these other distractions [reporters] may be interested in.”

Trump, who did not address reporters after the meeting, arrived on the second floor of the Capitol with McConnell just before 1 p.m. As the two strode side by side down a long hallway, a protester who had made his way into the press area shouted “Trump is treason!” and threw Russian flags in Trump’s direction.

The president’s feud with Corker laid bare the tensions between Trump and congressional Republicans that add to the uncertainty surrounding the GOP’s effort to advance tax cuts, its last-ditch attempt at a major policy accomplishment this year.

Trump has sharply criticized McConnell for failing to repeal and replace the Affordable Care Act. Republican senators have also thrown some rhetorical elbows at the president, with McConnell saying that Trump's limited experience in politics gave him "excessive expectations" about how quickly landmark legislation can pass.

Yet until Tuesday morning, both sides had appeared determined to move past their differences and project more harmony. Trump and McConnell sat down for lunch at the White House last Monday and came out for a 40-minute joint news conference afterward.

Republicans took an initial step toward passing a tax bill last week, when the Senate passed a budget resolution allowing them to pursue the plan without Democratic votes. The GOP also didn’t need Democratic votes to undo the ACA, but that effort still failed because of disagreements among Republican senators.

Brewing disputes over tax policy are threatening to disrupt if not defeat the tax endeavor in a similar way.

Earlier Tuesday, Corker stood by his previous description of the White House as an “adult day-care center” and his comment that Trump’s volatility could set the United States on a “path to World War III.” He also urged Trump to stop interfering in the debate over tax legislation.

Asked whether he regrets supporting Trump, Corker told CNN he would not do it again.

“The president has great difficulty with the truth on many issues,” he said. “He’s proven himself unable to rise to the occasion.”

Hours earlier, Trump had attacked Corker on Twitter for helping former president Barack Obama “give us the bad Iran Deal.” Trump also said Corker changed his plans to run for reelection in 2018 after he declined to endorse him.

In reality, Corker organized opposition to the Iran deal and voted against it. The senator and his top aide have said Trump offered his support for Corker’s reelection, and that after Corker announced that he would retire after next year, Trump called asking him to reconsider and to run again.

“Same untruths from an utterly untruthful president,” Corker tweeted Tuesday. He added the hashtag #AlertTheDaycareStaff, repeating an earlier description of Trump’s White House.

Corker said he did not speak to Trump at the lunch, and Trump did not speak to him.

“I was not a part of the lunch discussion,” Corker said. “I ate my lunch like I normally do.”

Republican lawmakers had entered the meeting with high expectations.

Speaker Paul D. Ryan (R-Wis.) said he was “glad” Trump was coming and argued the White House’s dispute with Corker will not hinder Republicans’ rewrite of the tax code.

“Put this Twitter dispute aside . . . All this stuff you see on a daily basis, Twitter this and Twitter that, forget about it,” Ryan told reporters at a news conference Tuesday.

Trump has promised changes to the tax code will not affect tax-deferred retirement plans, the mortgage interest deduction or the deduction for charitable contributions. Republicans like Corker say these promises raise expectations prematurely while making it more difficult for lawmakers to make up the revenue that will be lost to tax cuts.

When Trump addresses the GOP luncheon, “it’s important for him to convey to us the things that he thinks are priorities, and not only with respect to the tax bill, but some of the other things that we are currently working on,” said Sen. John Thune (S.D.), the third-ranking Republican senator.

Republicans continue to wrestle with health-care reform, particularly since Trump decided to end federal subsidies to offset lower-income Americans’ coverage costs. In response, a bipartisan coalition of senators offered a compromise bill authorizing those funds in exchange for giving states broader leeway in regulating coverage under the ACA.

Trump, who phoned Democratic and Republican lawmakers this month to push them to make a deal, has sent mixed signals on the plan, seeming to support it before backing away.

White House officials are now urging Senate Republicans to move the bill to the right by including provisions offering retroactive relief from the ACA’s insurance mandates for individuals and certain employers, according to people briefed on the talks.

“The White House has the ball right now,” said Sen. Lamar Alexander (Tenn.), the Republican who took the lead on negotiating the bipartisan package. “They’ve made some suggestions publicly about what they’d like to see in the bill. I’m for all of those things. The question is whether they can persuade Democratic senators to agree to that.”