White House attacks both Bush presidents after they reportedly refused to vote for Donald Trump

'Donald Trump represented everything that the Bushes abhorred', new book claims

Both former presidents have criticised Donald Trump in the past (AP)

The White House disparaged the legacies of the only two living Republican presidents to precede Donald Trump, after reports that both men castigated him in interviews last year and refused to vote for him.

Former President George HW Bush mocked then-candidate Trump as a "blowhard" and voted for a Democratic president, while the younger Bush worried aloud that Trump would destroy the idea of a Republican president in all but name, according to The Last Republicans. The book, by Mark Updegrove, is scheduled to go on sale later this month.

The White House response followed a CNN report about the new book in an extraordinary war of words involving three presidents from the same party.

"If one Presidential candidate can disassemble a political party, it speaks volumes about how strong a legacy its past two presidents really had," the White House wrote to CNN. It called the younger Bush's decision to wage war on Iraq "one of the greatest foreign policy mistakes in American history."

Updegrove interviewed the Bushes last year - long before Trump's inauguration - and found neither wanted to see the coarse, populist campaigner become president.

"I don't like him," George HW Bush told Updegrove in May 2016, according to CNN. "I don't know much about him, but I know he's a blowhard. And I'm not too excited about him being a leader."

A month earlier, Trump had famously cited himself as his own best foreign policy adviser. "Because I have a very good brain and I've said a lot of things," said the candidate, who had no diplomatic or military experience.

Upon learning this, Updegrove told CNN, George W Bush told him, "Wow, this guy doesn't know what it means to be president."

Those comments came as Trump neared the Republican nomination for president, having vanquished most other contenders, including another member of the Bush family, former Florida Gov. Jeb Bush.

George W Bush didn't expect Trump to win the general election, according to the author.

"When Trump started to rise, I think he became concerned because he saw this populism of Donald Trump getting in the way of America's position in the world," said Updegrove, who founded the National Medal of Honor Museum this year, after several years as director of the LBJ Presidential Library.

As he watched Trump's campaign, the younger Bush feared he - Bush - would "be the last Republican president," the author told CNN.

"And it wasn't just about Hillary Clinton becoming president," he said. "It was because Donald Trump represented everything that the Bushes abhorred."

Trump stood for rudeness, international isolationism and weak leadership in the eyes of the Bushes, according to CNN. This would track with a speech George W Bush gave last month, in which he didn't name the president but lamented these same vices and politics that "seems more vulnerable to conspiracy theories and outright fabrication."

Despite such reservations by the Bushes and other establishment Republicans, Trump, who has made more than 1,300 false or misleading claims in less than a year and almost constantly insults his many rivals, including upending the Republican primary with stinging attacks on "low energy" Jeb Bush, did win the presidency.

It's rare in the modern political era for former presidents to criticize their successors openly.

Trump's immediate predecessor, Barack Obama, whose Democratic administration has been endlessly berated by Trump, generally limits his rebuttals to attacks on Trump's policies -- never the man himself. And all five living ex-presidents partnered with Trump (who appeared via video feed) for a hurricane fundraiser just last month.

But not only did the Bush presidents lament the prospect of a Trump presidency, Updegrove told CNN, they even shunned their party's nominee on Election Day.

The younger Bush reportedly ticked "None of the above" when it came time to choose a president.

The elder Bush told the author he voted for Trump's rival Hillary Clinton, a Democrat.

The White House did not immediately respond to questions from The Washington Post.

A Bush family spokesman answered questions about Updegrove's book and the White House statement with a simple reply: "No comment, but thanks."

Washington Post