There is no reason to believe that any future Republican President would share the House Speaker’s view of Congress’s role. PHOTOGRAPH BY ZACH GIBSON / THE NEW YORK TIMES / REDUX

There are essentially two Republican parties right now: the Party of Donald J. Trump and the Party of House Speaker Paul Ryan—who has, nonetheless, endorsed Trump for President. One of the ways in which members of the Ryan faction delude themselves is by believing that Ryan’s policies would dominate if Trump were President and Ryan remained Speaker of the House.

The view of senior House Republicans with whom I talked over the past month, for a piece in this week’s magazine, was that Trump is “malleable,” as Congressman Tom Price, the chairman of the Budget Committee, put it. They believe that Trump, as President, can be pressed into service as a reliable signature for the Ryan agenda, which has been thwarted by a slow-moving Senate and by Obama’s veto pen. “I think we will work hand in glove, I really do,” Price told me on May 16th.

Ryan made this case explicitly in an Op-Ed endorsing Trump, which was published on the Web site of his home-town paper, the Janesville Gazette, on June 2nd. Ryan noted that when he took over as Speaker, last fall, his top priority was to fashion a detailed Republican policy agenda. The idea was to ignore the circus of the Republican Presidential primaries, which was sure to push the candidates into making reckless statements, and instead to have waiting at the end of the process a sober general-election platform that the Republican nominee could embrace. “The concept from the start was simple,” Ryan wrote. “If we had a Republican president ready to sign bills into law, what would we do?”

This instrumental view of the Presidency—that a Republican in the White House would serve more or less as an Autopen for Ryan’s ideas—rested, even apart from Trump, on two shaky assumptions.

The first was that Ryan could do a better job forging consensus than John Boehner, his predecessor, who was ousted by a band of House insurgents last September. Though it was overshadowed by the spectacle of the Presidential primaries, Ryan failed the first big test of unifying Republicans back in April, when he couldn’t pass a budget—something he’d promised he would do—because conservative Republicans refused to vote for it.

Ryan’s second assumption was that any new Republican President would respect a historical shift in the way that Republicans think about the balance of power between the executive and legislative branches. From 1969, the start of the Nixon Presidency, to 1993, the end of the George H. W. Bush Administration, when Republicans controlled the Presidency and Democrats dominated the House, the G.O.P. believed in a powerful executive, a view that was revived when George W. Bush took office. But in the Obama years, when Republicans’ base of power became more firmly rooted in Congress and, in their view, Barack Obama expanded the powers of the Presidency, Republicans became loud advocates of the primacy of the legislative branch.

Just yesterday, Ryan released a report about how Republicans can expand Congress’s authority, which the report argues has been allowed to “atrophy” as “the executive and judicial branches have vastly increased their power.”

As with Ryan’s optimistic predictions about House Republican unity, there is no reason to believe that a future Republican President would share the House G.O.P.’s view of Congress’s role. But it’s an especially absurd assumption when it comes to Trump, who has displayed authoritarian instincts and has argued that he will exceed Obama in using the powers of the executive branch.

More important, Trump’s agenda is not Ryan’s. The Speaker has been regularly unveiling policy reports on the Republican House agenda, and Trump, who seems oblivious to the Ryan project, has been shredding the ideas with his public comments. Two weeks ago, Trump argued that Gonzalo Curiel, a federal judge, couldn’t do his job because his parents were born in Mexico. A few days later, Ryan was scheduled to speak in a predominantly black neighborhood in Washington, D.C., about his new and much-touted policy proposals to address poverty. He ended up using the event to describe Trump’s claims about Curiel as “the textbook definition of a racist comment.” He immediately added, though, that he was still supporting him for President, in part because he thought that Hillary Clinton was worse.

This week, after the attack in Orlando, Trump reiterated his call for a ban on Muslims entering the U.S., and Ryan was forced to reiterate his opposition to the proposal. “I do not think a Muslim ban is in our country’s interest,” he said, at a press conference on Monday. “I do not think it is reflective of our principles. Not just as a party but as a country.” Ryan called for “a security test and not a religious test,” and pointed to a report on national security with sixty-seven recommendations that he had released just last Thursday. It was part of the same project he’s been working on all year, the one that he was hoping would lead to a package of legislation that a new Republican President would sign into law.

As he left Monday’s press conference, a reporter shouted a final question at Ryan: “Do you stand by your support of Donald Trump?” Ryan walked briskly through the scrum.

Another reporter laughed. “He didn’t answer,” he said. On Thursday, at his weekly press conference, Ryan did: he was standing by his endorsement of Trump for President.