Scottsdale, Arizona (CNN) The war in Iraq -- the issue that defined George W. Bush's presidency and haunted candidates from both parties on the 2008 campaign trail -- is back.

And this time it's creating headaches for Jeb Bush.

In his clearest declaration yet on his feelings about his brother's invasion of Iraq, the former Florida governor said Thursday that "knowing what we know now, ...I would not have engaged."

"I would not have gone into Iraq," he said.

The comments marked the fifth time this week that Bush sought to explain his position on Iraq -- a controversy that began Monday with a muddied expression of support for the war. Bush later tried to clean up the mess by calling the query -- one many believe he should have anticipated -- a "hypothetical," and by Wednesday, he acknowledged he would have done things differently in Iraq.

On Thursday, Bush argued that the invasion -- though perhaps inspired by faulty intelligence -- had been beneficial, saying the world was "significantly safer" without Saddam Hussein in power.

Photos: Jeb Bush's life Former Florida Gov. Jeb Bush waves as he takes the stage as he formally announces he is joining the race for president with a speech June 15, 2015, at Miami Dade College in Miami. Hide Caption 1 of 21 Photos: Jeb Bush's life Former Florida governor Jeb Bush shakes hands with attendees after speaking at the 42nd annual Conservative Political Action Conference on February 27 in National Harbor, Maryland. Hide Caption 2 of 21 Photos: Jeb Bush's life Bush takes a selfie with a guest at a luncheon hosted by the Chicago Council on Global Affairs on February 18 in Chicago. Bush delivered his first major foreign policy speech at the event. Hide Caption 3 of 21 Photos: Jeb Bush's life Bush hands out items for Holiday Food Baskets to those in need outside the Little Havana offices of CAMACOL, the Latin American Chamber of Commerce on December 17 in Miami. Hide Caption 4 of 21 Photos: Jeb Bush's life Bush waves to the audience at the Tampa Bay Times Forum in Tampa, Florida, on August 30, 2012, on the final day of the Republican National Convention. Hide Caption 5 of 21 Photos: Jeb Bush's life Bush (left) and wife Columba Bush attend the 2012 Lincoln Center Institute Gala at Frederick P. Rose Hall, Jazz at Lincoln Center on March 7, 2012, in New York City. Hide Caption 6 of 21 Photos: Jeb Bush's life President Barack Obama (left) speaks about Bush (center) while visiting Miami Central Senior High School on March 4, 2011 in Miami, Florida. The visit focused on education. Hide Caption 7 of 21 Photos: Jeb Bush's life Bush (left) speaks with Brazilian President in charge Jose Alancar during a meeting at Planalto Palace in Brasilia, April 17, 2007. Bush was in Brazil to speak about sugar and ethanol business. Hide Caption 8 of 21 Photos: Jeb Bush's life Then-Texas Governor Rick Perry (center) testifies as Bush (right) and then-Arizona Governor Janet Napolitano (left) listen during a hearing before the House Committee on Homeland Security on Capitol Hill October 19, 2005. Hide Caption 9 of 21 Photos: Jeb Bush's life Bush gives a thumbs up signal from his car as he leaves a local polling station after casting his vote in Coral Gables, Florida, November 5, 2002. Hide Caption 10 of 21 Photos: Jeb Bush's life Bush walks out of the West Wing after meeting with his brother, then-President George W. Bush, at the White House January 9, 2002. Governor Bush participated in the signing ceremony of the Everglades Protection Agreement. Hide Caption 11 of 21 Photos: Jeb Bush's life Then-Mexican President Vincente Fox (left) and Bush hold a press conference September 7, 2001, in Miami. Fox visited Florida to attend the Americas Conference and deliver a speech to speak about issues such as immigration. Hide Caption 12 of 21 Photos: Jeb Bush's life Then-President George W. Bush (right) is greeted by Jeb Bush on March 21, 2001, at Orlando International Airport in Orlando, Florida. President Bush was in Orlando to attend the American College of Cardiology Annual Convention. Hide Caption 13 of 21 Photos: Jeb Bush's life Bush speaks during a press conference at the Carandolet Government Palace in Quito, January 18, 2006. Bush and a businessmen delegation were in a two-day visit to talk about a free trade agreement. Hide Caption 14 of 21 Photos: Jeb Bush's life Bush speaks to reporters after meeting with the Florida State Cabinet at the Florida State Capitol Building November 16, 2000, in Tallahassee, Florida. Hide Caption 15 of 21 Photos: Jeb Bush's life Then-President George W. Bush (left) and Jeb Bush (right), raise their arms onstage following a rally at the Florida State Fairgrounds, October 25, 2000, in Brandon, Florida. Hide Caption 16 of 21 Photos: Jeb Bush's life Jeb Bush (left) and then-President George W. Bush stand with their arms around each other's shoulders at a rally in Miami, Florida, September 22, 2000. Hide Caption 17 of 21 Photos: Jeb Bush's life Then-President George W. Bush (right) and Jeb Bush go through the line for strawberries during a stop at the Stawberry Festival March 12, 2000 in Plant City, Florida. Hide Caption 18 of 21 Photos: Jeb Bush's life The Bush family, (left to right) former U.S. President George W., former Florida Governor Jeb, former President George H.W. and his wife Barbara, watch play during the Foursomes matches September 25, 1999 at The Country Club in Brookline, Massachusetts the site of the 33rd Ryder Cup Matches. Hide Caption 19 of 21 Photos: Jeb Bush's life Former President George H.W. Bush (second left), his wife Barbara Bush (left), their son Jeb Bush (center), then-first lady Hillary Clinton (second right), and former then-President Bill Clinton (right) look up to see the U.S. Army Golden Knights parachute team November 6, 1997 at the conclusion of the dedication ceremony of the George Bush Library in College Station, Texas. Hide Caption 20 of 21 Photos: Jeb Bush's life Portrait of the Bush family in front of their Kennebunkport, Maine house August 24, 1986. Pictured, back row: Margaret holding daughter Marshall, Marvin Bush, Bill LeBlond. Pictured, front row: Neil Bush holding son Pierce, Sharon, George W. Bush holding daughter Barbara, Laura Bush holding daughter Jenna, Barbara Bush, George Bush, Sam LeBlond, Doro Bush Lebond, George P. (Jeb's son), Jeb Bush holding son Jebby, Columba Bush and Noelle Bush. Hide Caption 21 of 21

The clumsy responses have surprised his allies and could reinforce concerns that Bush, who hasn't run for public office in more than a decade, is a rusty campaigner ill-equipped for the fast-moving news cycles of the social media age. It also revealed the difficulty Bush faces in presenting himself as his "own man" unburdened by his brother's controversial foreign policy decisions.

"The question about Iraq is not an illegitimate, hypothetical question. If you're sitting around pondering a Jeb Bush candidacy, it's the first obvious question that you have to be able to answer," said GOP strategist Steve Schmidt, who helped John McCain craft his message on Iraq during the 2008 election. "What his answer shows is the difficulty in moving beyond the Bush foreign policy in order to be able to attack the Obama-Clinton foreign policy, and to offer a vision for moving the country on to a firmer security footing."

The issue has become a significant distraction for Bush as he tours the nation ahead of a potential White House bid.

One Wednesday night, Bush found himself defending his brother's policies after a college student confronted him in Nevada. "Your brother created ISIS," she told him during an accusatory exchange on the current situation in the Middle East.

Bush's Republican rivals pounced at the opening.

'Really important question'

"I think it's a really important question, and I don't think it's just hypothetical," Kentucky Sen. Rand Paul, a GOP presidential hopeful, told CNN's Wolf Blitzer Wednesday. "I think even at the time invading Iraq was a mistake."

New Jersey Gov. Chris Christie noted he had no trouble answering the question directly and told CNN's Jake Tapper that in light of intelligence showing Iraq did not have weapons of mass destruction, he would not have gone to war. Ohio Gov. John Kasich took a similar stance in an interview with an Ohio newspaper.

Two GOP bundlers who couldn't speak with attribution because they are raising money for Bush said it was unnerving to see their candidate so prone to gaffes. Still, they shrugged it off as part of the campaign process.

While it has been a tough week for Bush, the return of the Iraq debate is also a reminder that the war perhaps looms even larger for Democratic frontrunner Hillary Clinton. Of all the candidates contemplating a presidential run, she is the only one in the field who has cast a vote to authorize military action in Iraq. Some Democratic voters still have not forgiven her for the vote -- cast when she served as a senator from New York -- which was a significant factor in her loss to Barack Obama during the 2008 Democratic presidential primaries.

"I thought I had acted in good faith and made the best decision I could with the information I had," Clinton, a former secretary of state, wrote in her book "Hard Choices." "And I wasn't alone in getting it wrong. But I still got it wrong."

Still, Clinton has not addressed her vote on Iraq since announcing her presidential bid, whereas Bush spent much of this week in the awkward position of having to clarify his views.

'Different decisions'

He went a step further at a political event in Nevada on Wednesday, saying, "given the power of looking back and having that, of course anybody would have made different decisions. There's no denying that."

He did not go so far as to say the war was a mistake, arguing that hypothetical questions about what he would have done are a disservice to the soldiers that fought and died in the conflict.

With months to go before GOP voters cast their first ballots in the early nominating contests, it's not clear that any of Bush's early stumbles will leave lasting damage.

"If you're going to make (mistakes) -- make them nine months out," said Tom Rath, a New Hampshire political operative who isn't aligned with a candidate. "I don't know that his position in the field has been impacted by this, but he was playing defense."

But Craig Robinson, a GOP activist who founded The Iowa Republican, said the flap over Bush's Iraq comments could further weaken his standing among GOP voters in the Hawkeye State -- not only because they raised questions about his polish as a candidate, but because they also created confusion about how his foreign policy approach would differ from his brother's.

Bush's original comment "resurrected the debate on Iraq, which is a losing argument," Robinson said.

"His refusal now to answer any similar questions after he claims to have misheard the original questions is even worse," Robinson said. "Nobody wants to go back and litigate war in Iraq, even now as the GOP is very hawkish when it comes to foreign policy. The problem with Jeb's answer, and now non-answer, is that we are left to wonder what his foreign policy would be if elected president."

While the war in Iraq was unpopular with the American public -- 75% said it was not "worth the loss of American lives and other costs," in a June 2014 CBS News/New York Times poll -- the conversation surrounding that corner of the globe has moved beyond the invasion in recent years. At Bush's political event in Nevada Wednesday, the first question was not about the war that was launched more than a decade ago, but rather the rise of the Islamic State militant group.

"What happened in 2003 is not a subject of a policy debate that affects what the U.S. is doing in Iraq today and what the U.S. will be doing in Iraq tomorrow," said Anthony Cordesman, an expert on security and Middle East policy at the Center for Strategic and International Studies. "The world is a very different place."

The discussion surrounding Iraq has evolved to include the fight against ISIS and broader sectarian, political and economic instability, he said.

"If Bush had been a little more articulate, people would've picked up on the fact that he was making that point," Cordesman said. But "if he can't rise above this issue, he hasn't got a prayer anyway."

The confrontation with the college student in Nevada about ISIS resulted in a new riff on him defending his brother's foreign policy.

"When we left Iraq, security had been arranged, Al Qaeda had been taken out. There was a fragile system that could have been brought up to eliminate the sectarian violence," he said, arguing that the rise of ISIS was President Obama's fault, not his brothers.