Last year, a poll of nearly 200 political science scholars, which has routinely placed Republicans higher than Democrats, ranked him 44th out of the 44 men who have occupied the post

At the two-year mark, it is usually clear how incumbents will leave their mark on the presidency. After the torpidity of the Eisenhower years, Kennedy made the office more youthful and glamorous. Johnson, that shrewd "Master of the Senate", brought the executive and legislative branches into closer alignment. Nixon consolidated more power in the White House, accelerating the trend the liberal historian Arthur M Schlesinger Jr dubbed "the imperial presidency."

Ford reversed much of that process, even going as far to drop the playing of "Hail to the Chief" when he made an entrance. The cardigan-wearing Jimmy Carter, who used to go from room to room turning off lights to save energy, suburbanised the White House. Reagan, who restored many of the ceremonial trappings, erased the lines between politics and entertainment.

Clinton, in the age of Oprah, made the office more empathetic, narrowing the emotional distance between the presidency and the people. Obama set a new standard for ethical behaviour - motivated in part by the African-American mantra of working twice as hard to get half as far - and also made the presidency more hip.

By abrogating behavioural customs, Donald Trump has made the presidency more uncouth and less trustworthy. By departing from executive and managerial norms, he has made domestic and foreign policy-making more impulsive and disorderly. By fraying traditional alliances, he has made the US presidency more isolated. By threatening to declare a national emergency in the funding row over his wall along the Mexican border, he has also indicated a willingness to discard constitutional norms that could mean exceeding constitutional limits.

The cumulative effect of this has been to make the Oval Office a focal point of perpetual turmoil and uncertainty, with the White House hostage to the changing whims and temper of its occupant. Governing sometimes feels secondary to winning political and cultural battles, and slaying opponents. His presidency has become a roiling permanent campaign.