Then there is what Trump said on Tuesday of Omarosa Manigault Newman, his former reality-television protege and White House staffer who is now scorned and telling all in her new book, Unhinged, and accompanying media tour. "When you give a crazed, crying lowlife a break, and give her a job at the White House, I guess it just didn't work out," Trump tweeted. "Good work by General Kelly for quickly firing that dog!" Animalistic slurs come easily to Trump, who over the past few years has likened a long list of perceived enemies to dogs - including former FBI director James Comey, former acting attorney general Sally Yates, former chief White House strategist Steve Bannon, former 2012 Republican presidential nominee Mitt Romney, Republican Senator Marco Rubio, journalist David Gregory and conservative commentator Erick Erickson. But in Trump's telling, Manigault Newman did not simply get fired "like a dog". She was a "dog" herself.

The President's calling a woman a dog - and not just any woman, but the highest-ranking African American who has served on his White House staff - drew stern condemnations. "Mr. President, it is beneath you and the office of the presidency to call any woman a dog," Democratic lawmaker Elijah Cummings tweeted. "It is degrading and demeaning, and I pray that you will stop this vulgar behavior. Our country is better than this." History is replete with authoritarian leaders who have sought to dehumanise individuals or groups of people by calling them animals. "In the fascist style of politics, one of the crucial elements is distinguishing 'us' from 'them'. We are intrinsically good; they are intrinsically bad, defective, subhuman, etcetera," said David Livingstone Smith, a philosophy professor who studies dehumanisation and racism and wrote a book on the subject, Less Than Human.

Former president Barack Obama is almost jerked off his feet as he shows off Bo, a Portuguese water dog with his daughters Malia, left, and Sasha, right, at the White House in 2009. Credit:AP Smith said dehumanising rhetoric was used by leaders to elicit fear and solidarity against some perceived existential threat from "others". Yet, while dogs are considered dirty in some cultures, such as in the Middle East, they are popular in the United States as household pets and are considered loyal and adoring. Smith suggested that a more apt slur in America would be calling someone a rat or pig or wolf. But Trump, an avowed germaphobe, has long had an aversion to dogs. "Donald was not a dog fan," his first wife, Ivana, writes in her memoir, Raising Trump. "When I told him I was bringing Chappy with me to New York, he said, 'No.' " But Ivana persisted, bringing her poodle with her when the couple moved in together.

"It's me and Chappy or no one," she recalls telling her husband Chappy, it turned out, did not much care for Trump either. Ivana wrote that when Trump approached her closet, her poodle would bark at him territorially. Loading Trump is the first modern US president not to have a dog - or any pet - in the White House. America's first president, George Washington, set the tone by breeding foxhounds. In recent decades, Ronald Reagan had Rex; George H.W. Bush had Millie; Bill Clinton had Buddy; George W. Bush had Spotty, Barney and Miss Beazley; and Barack Obama had Bo and Sunny.

The last president not to have a dog was William McKinley, who served from 1897 until his assassination in 1901. But even he had pets - a parrot and roosters. "Theodore Roosevelt sometimes would have over 30 pets in the White House because the president had such a love of God's creatures," said presidential historian Douglas Brinkley, who authored a Roosevelt biography. Brinkley suggested Trump has no pets "because he has no sense of giving and warmth and caring to any other animal but himself. Having no pet is another manifestation of his narcissism." Former US president George W. Bush with his dog Barney. Credit:AP Brooke Janis, who co-wrote First Dogs, a book about presidential pets, recalled former president Harry S. Truman's adage, "If you want a friend in Washington, get a dog."

"This is a President who needs a friend," Janis said of Trump. "Having a dog offers unconditional love, and that is something that this President desires so deeply and can't seem to find." The Washington Post