John Adams left the White House in a flurry of paperwork, working till midnight to fortify the United States against the next president, his political nemesis and friend, Thomas Jefferson. Each founder’s legacy was bound up in the other’s, setting a precedent for every president who followed them.



“These tensions in the American psyche go all the way back to the revolution,” said Barbara Perry, the director of presidential studies at the University of Virginia’s Miller Center.

Barack Obama also faces a successor radically opposed to his policies, philosophy and personality. Donald Trump’s unpredictability has left historians reluctant to say how much of Obama’s legacy he could erase, but they largely agree on one point. “Even the best-laid plans of presidents, including supreme court appointments, go awry,” Perry said.



Ken Mayer, a professor at the University of Wisconsin-Madison and author of a book on executive power, agreed on this point: “It’s going to be a bumpy ride.”

Presidents who repudiate their predecessors are not new. By the time he won the White House, the populist slaveowner Andrew Jackson (president from 1829 to 1837) had earlier in his life killed a duelist, invaded Florida and battled the British two weeks after the War of 1812 had ended. He succeeded the privileged, charmless John Quincy Adams, who studied at Harvard, crusaded for abolition and helped end the wars Jackson fought. They hated each other on principle and more.

“I don’t even know if Donald Trump has an ideology,” Perry said. “Since he, as a person and personality, seems so unpredictable, it’s really difficult to say anything with certainty.”

Trump will be able to quickly reverse some policy. He can immediately rescind Obama’s orders on immigration and the Dakota Access pipeline, for instance, just as Obama reversed a ban on abortion funding that had been restored by George W Bush, revoked by Bill Clinton, and created by Ronald Reagan. His powers are not limitless, though, as Obama found when he ordered the closure of Guantánamo Bay.

Barack Obama found closing the Guantánamo Bay prison camp easier said than done. Photograph: Brennan Linsley/AP

Obama found a host of obstacles to closing the prison, including addressing the fate of detainees and congressional resistance. “You can’t just say it’s closed and not worry about the subsequent issues that arise from closing it,” Mayer said. “It gets complicated in a hurry.” The result has been a slow reduction of detainees, from 242 to 59.

Mayer said presidents faced decisions “that are constitutionally legal but politically difficult”, noting how in 2001 the Bush administration backed down from its plan to block rules on arsenic in water. Almost 20 years earlier, Reagan’s EPA chief resigned amid accusations that she had mishandled waste cleanup – and after she had cut the agency’s budget by a fifth.

Perry said social security, affirmative action and abortion had similarly become standards of American life. The supreme court has consistently ruled in favor of the latter two, she noted, and justices have cited generations of precedent. “Are we really going to be able to turn back this cultural phenomenon?”

The healthcare reforms enacted by Obama – and modelled on Republican ideas – also fall into politically fraught territory, with 20 million people poised to lose health insurance. Even Mike Pence, the vice-president elect, embraced parts of the law. “They can imagine the blowback,” Mayer said. “They may find it’s not politically in their interest.”

For similar reasons, Richard Nixon was unable to dismantle Lyndon Johnson’s Great Society, and Bush failed to change social security. Republican Dwight Eisenhower not only left the Democrats’ New Deal intact, he expanded social security, raised the minimum wage and began new public works.

Republican Dwight Eisenhower, right, maintained and built on much of his Democratic predecessor’s approach. Photograph: William J Smith/AP

Presidents chipped away at their rivals, but usually over decades. Reagan eroded the Great Society, Clinton ceded ground to Republicans on welfare and justices hollowed out the Voting Rights Act. Conversely, Nixon supported environmental safeguards and justices ruled in favor of healthcare and affirmative action.

Even with Congress behind him, Trump cannot simply undo all regulations. The EPA’s findings on greenhouse gases, for instance, went through a long regulatory process – internal action, notices, proposed rules, public comment, etc; to change final regulations, the agency would have to return through the steps. Trump could, however, suspend guidelines and tentative regulations.



Republicans do not have a filibuster-proof majority, meaning that Trump will also have to deal with stubborn lawmakers and civil servants. His administrators could intimidate, reshuffle and put pressure on them, but laws protect federal employees. “Every president winds up feeling like the executive branch employees and cabinet secretaries are not as effective as they’d like,” Mayer said.

Trump will have more leeway on foreign policy, as Obama did when he steered the US away from Bush’s unilateral actions abroad. “We are looking at the potential for really radical changes,” said Paul Musgrave, a political scientist at the University of Massachusetts in Amherst.

“In that case, it’s not necessarily what America does as what it does not do,” he said. “Even ‘run of the mill’ crises – an eruption between Palestinians and Israelis, a global pandemic such as Ebola, or more aggression from China and the Philippines and Taiwan – create real dangers of misunderstandings, miscommunications and even of intentional escalations.”

Donald Trump’s unpredictability may mark a big change from the Obama era. Photograph: Kevin Lamarque/Reuters

Presidents have found it difficult to abandon pragmatism for ideology, especially abroad. Eisenhower took up Harry Truman’s philosophy of communist containment; Clinton embraced Reagan’s love of free trade; Obama preserved Bush’s expanding security state. But Musgrave said that even deals with many partners – for instance Nato or the Iran and Paris agreements – would be threatened by Trump’s refusal to act in good faith. “Short-term unpredictability promotes long-term unpredictability.

“For decades, the assumption has been that the United States is the global leader of last resort,” he said. “A lot of the truisms and rules that we have come to appreciate over the last 70 years are going to be modified.”

Perry said that some of this uncertainty was by design. “The founders created all these entry points,” she said, ways for constituents to impose their competing views on government. “It can be frustrating. The founders did not put a premium on rapidity.”

She also warned never to underestimate “the fickleness of the American electorate”.

“If he is doesn’t satisfy the so-called angry people who voted for him, who he ginned up in anger, what’s to prevent them from being angry at him?”