Senate Majority Leader Mitch McConnell, a Kentucky Republican, thinks so little of President Donald Trump as their relationship has “disintegrated” that he wonders whether Trump’s presidency can survive after a series of setbacks in recent months, per a new report from the New York Times.

The Times’ Alex Burns and Jonathan Martin wrote late Tuesday:

The relationship between President Trump and Senator Mitch McConnell, the majority leader, has disintegrated to the point that they have not spoken to each other in weeks, and Mr. McConnell has privately expressed uncertainty that Mr. Trump will be able to salvage his administration after a series of summer crises. What was once an uneasy governing alliance has curdled into a feud of mutual resentment and sometimes outright hostility, complicated by the position of Mr. McConnell’s wife, Elaine L. Chao, in Mr. Trump’s cabinet, according to more than a dozen people briefed on their imperiled partnership. Angry phone calls and private badmouthing have devolved into open conflict, with the president threatening to oppose Republican senators who cross him, and Mr. McConnell mobilizing to their defense.

The report, filled with explosive details, spells trouble for the two GOP heavyweights walking into a month of serious major political maelstroms with the debt ceiling, spending bill, tax reform, and a retry at healthcare looming–among other fights. Both Trump and McConnell themselves refused comment for the Times story, but McConnell spokesman Don Stewart said the president and majority leader had “shared goals” including “tax reform, infrastructure, funding the government, not defaulting on the debt, passing the defense authorization bill.”

“Still, the back-and-forth has been dramatic,” Burns and Martin wrote, pointing to how Trump ripped McConnell via Twitter multiple times in a “series of tweets” and “then berated him in a phone call that quickly devolved into a profane shouting match.” Burns and Martin wrote:

During the call, which Mr. Trump initiated on Aug. 9 from his New Jersey golf club, the president accused Mr. McConnell of bungling the health care issue. He was even more animated about what he intimated was the Senate leader’s refusal to protect him from investigations of Russian interference in the 2016 election, according to Republicans briefed on the conversation. Mr. McConnell has fumed over Mr. Trump’s regular threats against fellow Republicans and criticism of Senate rules, and questioned Mr. Trump’s understanding of the presidency in a public speech. Mr. McConnell has made sharper comments in private, describing Mr. Trump as entirely unwilling to learn the basics of governing.

Perhaps more importantly, though, Burns and Martin report that McConnell has privately wondered aloud whether Trump’s presidency will survive. They wrote:

In offhand remarks, Mr. McConnell has expressed a sense of bewilderment about where Mr. Trump’s presidency may be headed, and has mused about whether Mr. Trump will be in a position to lead the Republican Party into next year’s elections and beyond, according to people who have spoken to him directly. While maintaining a pose of public reserve, Mr. McConnell expressed horror to advisers last week after Mr. Trump’s comments equating white supremacists in Charlottesville, Va., with protesters who rallied against them. Mr. Trump’s most explosive remarks came at a news conference in Manhattan, where he stood beside Ms. Chao.

Elaine Chao, McConnell’s wife and Trump’s Transportation Secretary, deflected on the matter when asked about it by reporters, saying: “I stand by my man — both of them.”

When CEOs abandoned a council built by White House National Economic Council director Gary Cohn and Trump son-in-law and adviser Jared Kushner in the wake of the president’s Charlottesville response, Burns and Martin report that McConnell comforted them.

“Mr. McConnell signaled to business leaders that he was deeply uncomfortable with Mr. Trump’s comments: Several who resigned advisory roles in the Trump administration contacted Mr. McConnell’s office after the fact, and were told that Mr. McConnell fully understood their choices, three people briefed on the conversations said,” Burns and Martin wrote.

What’s more, Trump’s decision to bash many specific Senate Republicans publicly–the latest is Sen. Jeff Flake (R-AZ), whose state Trump is visiting on Tuesday evening for a campaign rally, at which he may again bash Flake–has irritated McConnell, the Times reporters wrote. They write that the GOP’s senators, Flake’s colleagues, “would stand up for” Flake should Trump rail on him.

When it comes to the Senate, there’s an Article 5 understanding: An attack against one is an attack against all,” Sen. Lindsey Graham (R-SC), a frequent target of Trump’s ire, told the Times, referring to what the Times says is “the NATO alliance’s mutual defense doctrine.” In other words, any Trump attack on any one Republican would spark a defense from all Republicans for that member, per Graham and the Times.

The paper points to Senate Leadership Fund, a McConnell-backed Super PAC that has been carpet-bombing pro-Trump conservatives in other races, such as in Alabama, dropping a major attack against former state Sen. Kelli Ward of Arizona–a doctor who is challenging Flake in the primary after coming up short against Sen. John McCain (R-AZ) last year. The Times adds:

The fury among Senate Republicans toward Mr. Trump has been building since last month, even before he lashed out at Mr. McConnell. Some of them blame the president for not being able to rally the party around any version of legislation to repeal the Affordable Care Act, accusing him of not knowing even the basics about the policy. Senate Republicans also say strong-arm tactics from the White House backfired, making it harder to cobble together votes and have left bad feelings in the caucus.

They point to instances with Sens. Lisa Murkowski (R-AK) and Shelley Moore Capito (R-WV) as particularly problematic. With the former, Trump’s Interior Secretary Ryan Zinke threatened to withhold federal funding for Alaska if she did not vote for Obamacare repeal, and with the latter the White House would not let the senator accompany the president on Air Force One to the annual Boy Scouts jamboree in her home state if she did not commit to voting to repeal Obamacare.

McConnell is now fully committed to firing back at Trump, and protecting his GOP senators. Burns and Martin wrote:

In a show of solidarity, albeit one planned well before Mr. Trump took aim at Mr. Flake, Mr. McConnell will host a $1,000-per-person dinner on Friday in Kentucky for the Arizona senator, as well as for Senator Dean Heller of Nevada, who is also facing a Trump-inspired primary race next year, and Senator Deb Fischer of Nebraska. Mr. Flake is expected to attend the event.

McConnell allies like former Sen. Judd Gregg of New Hampshire and former Republican National Committee finance chair Al Hoffman are quoted as well, making ominous predictions about Trump.

“Failure to do things like keeping the government open and passing a tax bill is the functional equivalent of playing Russian roulette with all the chambers loaded,” Gregg said of Trump, blaming him for in the Times’ words “undermining” congressional leaders, adding that if Trump “can’t participate constructively” the House and Senate would take matters into their own hands.

“Ultimately, it’s been Mitch’s responsibility, and I don’t think he’s done much,” Hoffman said, slightly critical of McConnell before adding that he believes McConnell will outlast Trump in this stalemate.

“I think he’s going to blow up, self-implode,” Hoffman said of the president, per the Times. “I wouldn’t be surprised if McConnell pulls back his support of Trump and tries to go it alone.”

Later in the piece, an ex-McConnell chief of staff–there are several of them who publicly defend the majority leader–said that Trump risks impeachment if he targets Flake and Sen. Dean Heller (R-NV), another establishment Republican who faces a primary challenge next year.

“The quickest way for him to get impeached is for Trump to knock off Jeff Flake and Dean Heller and be faced with a Democrat-led Senate,” Billy Piper, the ex-McConnell chief of staff who is now a lobbyist, said.

Piper’s logic does not necessarily fit the facts: There is a 52-member slim GOP majority in the Senate right now, but the map in 2018 is very favorable to Republicans. In 10 states that Trump won in 2016, weak incumbent Democratic senators face re-election. Several more states offer potential opportunities for GOP pickups as well, meaning even if the GOP risks it in Nevada and Arizona by trading Flake and Heller for stronger Republicans, potential losses would be offset by significant pickups elsewhere.

Nonetheless, the battle between Trump and McConnell continues into a deeper stalemate walking into a packed September. Burns and Martin wrote:

An all-out clash between Mr. Trump and Mr. McConnell would play out between men whose strengths and weaknesses are very different. Mr. Trump is a political amateur, still unschooled in the ways of Washington, but he maintains a viselike grip on the affections of the Republican base. Mr. McConnell is a soft-spoken career politician, with virtuoso mastery of political fund-raising and tactics, but he had no mass following to speak of. Mr. McConnell, while baffled at Mr. Trump’s penchant for internecine attacks, is a ruthless pragmatist and has given no overt indication that he plans to seek more drastic conflict. Despite his private battles with Mr. Trump, Mr. McConnell has sent reassuring signals with his public conduct: On Monday, he appeared in Louisville, Ky., with Steven Mnuchin, the Treasury secretary, for a discussion of tax policy.

And outside of what McConnell himself does, his members are more boldly criticizing the president. Senate Foreign Relations committee chairman Sen. Bob Corker (R-TN), for instance, ripped Trump’s response to Charlottesville–something the Times implies comes from a green light from McConnell that it’s open season on Trump now.

“Mr. McConnell’s Senate colleagues, however, have grown bolder. The combination of the president’s frontal attacks on Senate Republicans and his claim that there were ‘fine people’ marching with white supremacists in Charlottesville has emboldened lawmakers to criticize Mr. Trump in withering terms,” Burns and Martin wrote. “Senator Bob Corker of Tennessee rebuked Mr. Trump last week for failing to “demonstrate the stability nor some of the competence” required of presidents. On Monday, Senator Susan Collins of Maine said in a television interview that she was uncertain Mr. Trump would be the Republican presidential nominee in 2020.”