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Jeb Bush's fight with Donald Trump comes with big risks

The bigger concern for Bush, however, should be where the conversation goes next.

After a brief break to explore various side projects, Jeb Bush and Donald Trump are back to their natural state: fighting each other. 

The topic at hand is whether it’s fair to blame President George W. Bush for not doing enough to prevent the 9/11 terrorist attacks or whether such claims are out of bounds in a Republican primary. 

“When you talk about George Bush, I mean, say what you want, the World Trade Center came down during his time,” Trump told Bloomberg on Friday, kicking off the dispute.

“How pathetic for [Trump] to criticize the president for 9/11,” Bush tweeted in response. “We were attacked & my brother kept us safe.” His campaign followed up with a web video highlighting Trump’s well-established lack of depth on foreign policy.

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Trump took things further in subsequent interviews by boasting on Fox News he would have prevented the attacks with his “extremely tough” plan to combat illegal immigration. The hijackers used legal visas to enter the country and carry out their plot, although the 9/11 Commission identified red flags that might have been used to deny some entry or deport them once they had entered the country. Trump followed up by tweeting out a BuzzFeed article noting that the billionaire had actually issued a fairly prescient warning about Osama bin Laden while weighing a presidential run with the Reform Party. 

The debate -- and Bush’s awkwardly worded response on Twitter -- put Trump in the odd position of rallying liberals who have long objected to the “kept us safe” version of events. On Monday, progressives on social media circulated a piece in The Atlantic by Peter Beinart listing the myriad complaints Bush’s own counterterrorism officials raised about the run-up to 9/11. Conservative commentators, meanwhile, defended the former president and complained that President Clinton hadn’t done enough to stop bin Laden. 

Just like the last time Trump and Bush went at it, each one has various reasons to get into the fray. Trump has feuded with virtually the entire field, but has always seemed to relish going after Bush the most, whose establishment background, pricey donors, and immigration positions make him an easy foil.

As for Bush, he does not like when anyone criticizes his family and, after initially agonizing over how to handle his brother, has tended toward defending him. He’s hosting an event with his presidential sibling and father in Texas late this month.

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Bush's advisers left the last Republican debate crowing to reporters about the applause Bush received after he declared that his brother “kept us safe" and may see some upside in recreating the moment. Last month, Bush's team was concerned that Trump's constant sniping was dragging their candidate down, but it's possible that Trump does more damage by ignoring him. Lately, Trump has devoted the most firepower to Rubio – Bush’s chief establishment rival – and the sparring match may have served to elevate him. In the latest WSJ/NBC News poll on Monday, Rubio stood in third place with 13% support while Bush was stuck in fifth place at 8% support.

A new feud could help put Bush back in the spotlight as the leading Trump opponent.  

The danger for Bush is that even if you assume his take on 9/11 is politically safe territory for now, there’s no guarantee the conversation stays there.  

For one, the discussion comes at an especially sensitive time for Republicans as they prepare for a showdown in the House with Hillary Clinton over another "9/11," the 2012 murder of four Americans in Benghazi. Democrats have argued that the committee looking into Benghazi exists solely to drag down Clinton’s political standing, and they got a major boost when Republican Majority Leader Kevin McCarthy credited it with doing just that on Fox News. More difficulties have followed, including another Republican congressman saying something similar, a Benghazi committee staffer claiming they were forced out for objecting to its focus on Clinton, and a fresh dispute over whether the committee issued misleading claims about Clinton’s handling of classified information. Committee chairman Trey Gowdy has called this period “among the worst weeks of my life,” which is not exactly what Republicans want to hear days before Clinton testifies.

RELATED: Will Republicans overplay their hand on Benghazi? 

Mark down Bush’s decision to reopen the debate over his brother’s record as another item on Gowdy’s list of woes. If it’s taboo to suggest a sitting president might bear some blame for not stopping an unprecedented wave of terror on the homeland that killed thousands, it raises the obvious question of why an attack on American officials in the middle of a war zone overseas should be fodder for constant, sometimes grotesque, political attacks.

Sure enough, CNN’s Jake Tapper asked Bush exactly that on Sunday: “If your brother and his administration bear no responsibility at all, how do you then make the jump that President Obama and Secretary Clinton are responsible for what happened at Benghazi?” Tapper said.

“The question on Benghazi which, is hopefully we'll now finally get the truth to, is was the place secure?” Bush, who seemed caught off guard, responded. “They had a responsibility, the Department of State, to have proper security.” 

As Tapper noted, though, the issue of whether it’s a leader’s responsibility “to have proper security” is exactly what Trump had raised. “That's kind of proving the point of the critics I was just asking about,” he said.  

The bigger concern for Bush, however, should be where a debate over 9/11 goes next. As Trump appears clever enough to recognize, it’s a short hop and skip from an argument over what the Bush administration did before the attacks to what they did afterwards. 

“Jeb, why did your brother attack and [destabilize] the Middle East by attacking Iraq when there were no weapons of mass destruction? Bad info?” Trump tweeted on Sunday.

WATCH: 'Morning Joe' panel offers advice to Jeb on handling Trump

Bush has never looked comfortable debating the run-up to the Iraq War, a trend that dates back to before he launched his campaign and has continued throughout the race. It will take a deft hand to keep the story on Trump’s lack of foreign policy knowledge – which one expects the billionaire’s supporters have largely digested at this point – without drifting towards the costly invasion that Bush himself labeled a "mistake" in last month's debate. 

The former Florida governor is now at a critical point in his campaign. If he doesn’t make a move in the polls soon or drag down Trump, he risks a panic that could swing establishment support to Rubio or other candidates. Nothing in the race so far has suggested that re-fighting his brother’s political battles is the key to success. Can he afford to waste another week on it?