Donald Trump has succeeded against all odds as a political force in America. But after his raucous campaign-style speech in Arizona Tuesday night, in which he implicitly attacked the state’s two Republican senators, President Trump is wading ever-deeper into uncharted waters.

Never before has an American president intentionally disavowed members of his party before they abandoned him, historians say.

And thus a critical question emerges just seven months into Mr. Trump’s presidency: Can he govern successfully, despite growing alienation from key members of his own party?

Republicans will have to pass legislation on their own, probably with some Democratic votes, and trust that Trump is willing to sign it – even if it doesn’t meet his demands, such as funding of the border wall, says presidential scholar Cal Jillson of Southern Methodist University in Dallas.

“At the end of the day, he [will] sign something that keeps the government open and functioning, otherwise there will just be too much wailing and gnashing of teeth,” says Mr. Jillson, referring to two critical legislative actions looming – the raising of the debt ceiling and the funding of the government into the next fiscal year, which begins Oct. 1.

But in the current state of Trump-GOP tension, passing larger initiatives such as health and tax reform and funding for infrastructure may well be too long a throw, he adds.

In a 77-minute stem-winder Tuesday night, Trump seemed to be channeling his populist-nationalist former chief strategist Steve Bannon as he came out with one eye-popping statement after another: He threatened to shut down the government if Congress didn’t fund the wall. He said the North American Free Trade Agreement would probably be terminated. He hinted at a pardon for the controversial former Arizona sheriff, Joe Arpaio.

And perhaps most shockingly, he went after the state’s two Republican senators, though not by name: John McCain and Jeff Flake. Both have run afoul of Trump – Senator McCain in his surprise, decisive vote against consideration of legislation to repeal and replace the Affordable Care Act; and Senator Flake, who recently published an anti-Trump book, “Conscience of a Conservative: A Rejection of Destructive Politics and a Return to Principle.”

The shock comes not in Trump’s upset, but in his decision to go after two senators who help make up the Senate’s slim two-seat Republican majority – despite apparent warnings by presidential aides not to attack them. Senator Flake is up for reelection next year, and faces a primary. If he loses the primary, Democrats could take the seat, political analysts say. McCain faces a serious health challenge, and Trump did not acknowledge that or wish him a speedy recovery. Nor did he bring up Monday's Navy accident on the USS John S. McCain, named for the senator’s father and grandfather, that killed several sailors.

Trump even appeared to mock his own aides: “Please, please, Mr. President, don’t mention any names,” he said before hinting at criticism of McCain. Then he went on to Flake. “And nobody wants me to talk about your other senator, who’s weak on borders, weak on crime, so I won’t talk about him,” Trump said.

Earlier in the day Tuesday, a New York Times story reported that the relationship between Trump and the Senate GOP leader, Mitch McConnell, had deteriorated to the point where they had not spoken in weeks also certainly fueled the president’s fiery rhetoric.

“McConnell, in private, doubts if Trump can save presidency,” read the headline.

That schism alone could be enough to sink Trump’s agenda. On Wednesday, McConnell did damage control, releasing a statement saying he and Trump have shared priorities.

“We have a lot of work ahead of us, and we are committed to advancing our shared agenda together and anyone who suggests otherwise is clearly not part of the conversation,” McConnell said in a statement.

The White House also issued a statement, saying the two men “remain united on many shared priorities, including middle class tax relief, strengthening the military, constructing a southern border wall, and other important issues” and would be holding previously scheduled meetings on these issues after Congress’ August recess.

Still, the president’s relationship with other Republicans has been increasingly rocky. His ties to House Speaker Paul Ryan have been transactional at best since Trump launched his political career. Sen. Ben Sasse of Nebraska has been a “never Trumper” from Day One, though has consistently voted with his party when it mattered. Others have grown increasingly bold in questioning Trump’s fitness for office, including Senate Foreign Relations Committee Chairman Bob Corker of Tennessee and Senator Susan Collins of Maine.

But Trump is undeterred, and seems energized by the conflict – the upstart president versus the “swamp.”

During his speech Tuesday, Trump called on Senate Republicans to get rid of the filibuster and thus the need to garner 60 votes for most legislation. Senator McConnell has rejected that idea forcefully, looking ahead to a time when Republicans will inevitably be in the minority again and will need legislative tools to combat the Democrats. Trump has no interest in such far-sighted planning.

And so the potential for intra-party stalemate looms – a source of alarm to party regulars, but not those looking to break the Washington establishment, foremost among them Trump supporters.

“He seems on a collision course with his own party,” says historian David Pietrusza. “Many of his more convinced followers – and some not so convinced – welcome this, as so many voters cheer any opposition to the so-called ‘swamp.’”

Mr. Pietrusza identifies a series of 19th -century presidents he calls “accidental” – John Tyler, Millard Fillmore, Andrew Johnson, and Chester Arthur, all of whom assumed the highest office after their predecessors died.

“All failed to hold their party’s trust,” he says. “And all were denied nomination for another term.”

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Pietrusza notes that the power of the president has increased greatly since the 19th century, but concludes that when it comes to guiding an agenda through Congress “declaring war on one's own party in the Congress is definitely a fool's errand.”

Like many aspects of Trump’s presidency, the intra-party feud is unprecedented. But no one can predict with absolute certainty that, going forward, Trump won’t be able to make something of his time in office. On national security policy, in particular, he has wide-ranging powers. And after all, he has gone farther in his political career than most predicted, perhaps even he himself.