Both Bush presidents bash 'blowhard' Donald Trump as unfit for the presidency

However, unlike his father, George W. Bush did not vote for Democratic presidential nominee Hillary Clinton in the 2016 election and instead left the top of his ticket blank.

His son, former President George W. Bush, also had some harsh words for his Republican successor: "This guy doesn't know what it means to be president".

George W. Bush's comments were slightly less inflammatory than his father's, although he told Updegrove that while he thought Trump could unify the country, it would require "humility", CNN reported. "I don't like him", Bush said in May 2016. "I don't know much about him, but I know he's a blowhard", said Bush, now 93.

Updegrove, the founding chief executive of the National Medal of Honor Museum and the former director of the Lyndon Baines Johnson Presidential Library and Museum, came up with the book's title after a comment from the younger Bush during the 2016 election season.

George W Bush, adding to his remarks that Mr Trump "doesn't know what it means to be president", said "you can either exploit the anger, incite it, or you can come up with ideas to deal with it". "It was because Donald Trump represented everything that the Bushes abhorred", Mr Updegrove told CNN.

"The Last Republicans", published by HarperCollins, will be out November 14.

The book's author spoke with George W. Bush as Trump was sewing up the Republican nomination.

In the book, Updegrove writes that the younger Bush did not think Trump would win when he first entered the presidential race.

The White House responded with a scathing statement calling the Iraq war, started under the 43rd President, "one of the greatest foreign policy mistakes in American history".

The book, "The Last Republican", was written by Mark D. Updegrove with the cooperation of both former presidents Bush and is due to be released November 14 by HarperCollins.

As the previous Republican president before Barack Obama took office, he told the author: "You know, I fear that I will be the last Republican president". I always liked him, but I didn't like him so much for a while because I thought he hurt George. "I think he pushed things a little too far right".

"The fact that there was any doubt in anyone's mind about who the president was blows my mind", he said.

They "didn't make one fucking decision", he told Updegrove.