This Bloomberg article argues with some force that Trump has, over 7 months, demonstrated an inability to be an effective President, as laid out in Richard Neustadt’s 1960 political science classic, Presidential Power.
Neustadt’s thesis was that the Presidency was inherently weak, based on its Constitutional powers. An effective presidency came less from the Constitution than the Chief Executive’s ability to articulate policy and vision, and persuade and influence governmental partners (the public, his party, his own Administration leadership, the bureaucracy, the courts, and the Congress) to go along with what he wants.
Trump’s ramshackle appointment process, his division of others into his minions or his enemies, his disdain for policy over polemic, his preference for rallies of fans over engaging the nation, his tendency to issue orders to Congress rather than make them his allies, and the anger / insecurity / ad libbing issues that continue to distract from his goals and derail any actions he does actually take, have made him (the author posits) a significantly weaker president than even the powers of the office allow.
Which isn’t to say he doesn’t have an ability to work mischief (as his environmental and immigration policies demonstrate, as well as his actions to alienate most US allies), just that it will tend to be more from thrashing about in impulsive and angry jerks than from a concerted, careful effort. Indeed, a lot of what is actually being accomplished is more at the hands (and will) of the individuals Trump has put into positions of power, than any coherent “Trump Agenda.” The man who rode into office claiming to be the consummate business leader and the master of the Art of the Deal, has shown himself an awful salesman, let alone CEO.
Which carries with it its own costs. It means Trump’s explicit effect is likely to be far less than people have feared. But his implicit effect, his inability to articulate and carry through policy and vision that carries the nation, that can address the inevitable crises, that can actually work — there Trump’s weakness and inability could spell disaster for the United States for years to come.