Mary L. Trump, whose best-selling book calls her uncle President Trump “the world’s most dangerous man,” said in an interview with The Washington Post that she plans to do “everything in my power” to elect Democrat Joe Biden as president, but hasn’t yet talked to his campaign.

Speaking Monday on The Post Live program with reporter Robert Costa, the president’s niece acknowledged that she had not obtained permission to use a series of incendiary quotes from her aunt Maryanne Trump Barry. In the book, Mary Trump quotes Maryanne as saying that Donald Trump was a “clown” who would never get elected.

Asked whether Maryanne knew her quotes would be in the book, Mary Trump said that they came from conversations that took place before she planned to write a book. She said that she hadn’t talked to Maryanne since the book was published and said she would not be surprised “if she never contacted me, and I think that’s fair. I understand why she would not want to.”

Maryanne Trump Barry could not immediately be reached for comment.

Mary Trump, 55, who was trained as a clinical psychologist, observed her uncle throughout her childhood and has watched him closely as president. She has said that she believes he is unfit to serve in the White House.

The president has called the book untruthful, and his family tried unsuccessfully to stop its publication. The book, “Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man,” was published July 14. Mary Trump has said she hopes it influences voters to turn her uncle out of office.

“I haven’t spoken to anybody on the [Biden] campaign,” Mary Trump said. “But I’ll do everything in my power to make sure that Joe Biden gets elected, that I will do.”

Mary Trump said that while she did not try to diagnose her uncle, she said her background as a clinical psychologist gave her confidence in her grim assessment of him.

“What I was trying to do early in the book was to give people a sense of things that might be going on, to give people a picture of some of the symptomatology that we’re seeing,” Mary Trump said.

“And also point out the idea that there really is probably no single diagnosis. There’s so much overlap. His behaviors are often complex and often seem self-defeating that, you know, we need to dig a little deeper. And the way to do that, other than, you know, obviously looking at his behavior is to look at his family history, which is something I believe I had some insight into.”

Mary Trump wrote in her book that a friend of Donald Trump named Joe Shapiro took the SAT for him to enable Trump to gain admission to the University of Pennsylvania. She acknowledged in the interview that she doesn’t know who the person is, but she said the point she sought to make is her belief that Donald Trump paid the person to take the test.

No proof has emerged to uphold the allegation. A friend of Donald Trump with the same name went to Penn with him, but that person is deceased, and his sister and his widow both told The Post that he would have never taken a test for Trump.

Mary said it was a different Joe Shapiro who took the test. She said she got the information from a family source whom she did not identify.

“The name Joe Shapiro is not uncommon in New York City,” Mary Trump said. “So the reason I’m confident is because I have been told this story by somebody who was there at the time and was well aware that this happened.”

Asked whether Maryanne Trump Barry is the person who told her the anecdote, she said, “I prefer not to say who it is.” She added, “It’s somebody who would have had absolutely no reason to make it up.”

While Mary Trump’s book is an all-out attack on her uncle, much of it centers on the tragic story of her father, Fred Trump Jr., who died of an alcohol-related illness when she was 16 years old in 1981. In the book, she blames Donald Trump and his father, Fred Trump Sr., for mistreating her father, who gave up his dream to be an airline pilot to accede to demands to work in the family business.

Mary Trump said her first memory of her father, when she was about two and a half years old, was of him pointing a gun at her mother. “He was quite drunk,” she said.

She said that while many people have fond memories of her father, she was born after he had already descended into alcoholism. Earlier in her life, she said, she bought into the Trump family idea that her father was a failure due to his own circumstances. Only later, after learning of his exploits as a pilot and other activities, did she realize that he was a gracious man with many friends who cared deeply about other people.

“I never met that man,” she said. It is to her “shame,” she said, that she believed the family rhetoric that her father “was basically the sum total of his disease of alcoholism.”

Mary Trump was involved in a bitter fight over her inheritance of a portion of the estate from Fred Trump Sr. She and her brother had believed they would get something close to the amount that would have gone to their father, if he had lived. Instead, they were given a much lesser amount, and she agreed to a confidential settlement in 2001. She has not said how much she received in the settlement.

Donald Trump’s younger brother, Robert, filed a complaint seeking to stop the book on grounds that it violated the confidential settlement in the inheritance case, but a New York court ruled that the book could be published.