Jeb Bush and Donald Trump are involved in a bitter feud over 9/11

Former Florida Gov. Jeb Bush (R) and Donald Trump are engaged in a heated back and forth relitigating blame for the September 11, 2001, terror attacks on US soil.

In an interview Friday with Bloomberg, Trump suggested that President George W. Bush, Jeb Bush's brother, was partially to blame for the September 11 terrorist attacks on the World Trade Center and the Pentagon because they happened during his presidency.

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That drew a response from Jeb Bush, who called Trump's comments "pathetic," and the two continued to trade barbs over the weekend.

And on Sunday, Jeb Bush struck hard, defending his brother's record while saying that Trump was treating his candidacy as if he was "still on 'The Apprentice.'"

George W. Bush "united the country, he organized our country, and he kept us safe. And there's no denying that," Bush told "State of the Union" host Jake Tapper.

"I don't know why he keeps bringing this up," Bush said of Trump on CNN. "It doesn't show that he's a serious person as it relates to being commander-in-chief and being the architect of a foreign policy. Across the spectrum of foreign policy, Mr. Trump talks about things as though he's still on 'The Apprentice.'"

Bush also brushed off the legitimacy of Trump's candidacy, saying the former reality-television star's policy proposals were so thin that he almost seemed like he was only pretending to be a real candidate.

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"For him, it looks as though it's -- he's an actor playing a role of the candidate for president," Bush said. "Not boning up on the issues, not having a broad sense of the responsibilities of what it is to be a president."

Trump immediately took to Twitter to respond, doubling down on a previous assertion that President George W. Bush's invasion of Iraq was partially to blame for the current lack of stability in the Middle East.

Jeb, why did your brother attack and destabalize the Middle East by attacking Iraq when there were no weapons of mass destruction? Bad info?

The two Republican presidential candidates have spent the last several days criticizing each other on the issue.

After Jeb Bush called Trump's rhetorical jabs "pathetic" on Friday Trump doubled down on his comments on Saturday, telling The Washington Post that President George W. Bush ignored warning signs from the CIA and didn't facilitate coordination between the federal intelligence and security agencies in a way that could've minimized damage before or during the attack.

The 9/11 Commission Report, the comprehensive government investigation that laid out the failures leading to the 2001 attacks, revealed that the seeds for the attacks were sown beyond George W. Bush's tenure. The report found that several of the hijackers were already operating covertly in the United States before Bush even took office. The report also said the intelligence agencies knew an attack of some kind was "imminent."

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