After a week’s worth of stumbling statements about the Iraq war, in the minds of many Americans the signature failure of his brother’s presidency, Jeb Bush on Thursday shared a fourth opinion in as many days on the wisdom of the 2003 invasion.

Given knowledge of the puniness of Saddam Hussein’s weapons programs at the time, Bush said, “I would have not gone into Iraq.”

The former Florida governor insisted, however, that the war had made the world “significantly safer”.

He is expected to announce a presidential candidacy later this spring.

The firm “no” on the question of informed invasion came after days in which Bush issued contradictory statements about the war. On Monday he told an interviewer he would have invaded Iraq, even “knowing what we know now”. On Tuesday he said he had “interpreted the question wrong” and also said he would not answer a “hypothetical” because it would be a “disservice” to members of the military.

On Thursday, on the sidelines of a Republican National Committee meeting in Arizona, Bush grudgingly offered a new take.

“If we’re all supposed to answer hypothetical questions, ‘Knowing what we know now, what would you have done?’ – I would have not engaged, I would have not gone into Iraq,” Bush said.

Bush then spoke approvingly of the war: “That’s not to say that the world is [not] safer because Saddam Hussein is gone. It is significantly safer. That’s not to say that there was [not] a courageous effort to bring about a surge that created stability in Iraq. All of that is true.”

Bush’s brother, George W Bush, launched the March 2003 invasion of Iraq as president and declared two months later that “major combat operations” had ended. The US has added troops, trainers and advisers to Iraq this year, up to a stated limit of 3,000.

Jeb Bush has defended the Iraq war despite broad and sustained public opposition to it. More than half of Americans have called the war a mistake in Gallup polling for at least the last 10 years. June 2014 polling measured the split at 57% to 39%, calling the invasion a mistake.

For the self-evident political risks the war and its legacy pose for Jeb Bush, the potential presidential candidate has not taken pains to distance himself from the decision to invade Iraq or from his brother.

On Monday, Bush told Fox News he and his brother shared a perspective on the Iraq conflict. “News flash to the world, if they’re trying to find places where there’s big space between me and my brother, this might not be one of those,” he said.

Last week, Bush said he turns to his brother for foreign policy advice. “What you need to know is that who I listen to when I need advice on the Middle East is George W Bush,” he was quoted as telling a private gathering in Manhattan.

George W Bush has a 74%-21% favorability rating among Republican primary voters, according to a February poll by Public Policy Polling.

Jeb Bush’s early fumbling on the Iraq question – one for which he was expected to have developed a pat answer – set off a race among potential primary opponents to issue direct statements about the invasion.

Senator Marco Rubio, who declared his presidential candidacy last month, took the “knowing then what we know now” question from an interviewer on Wednesday.

“Not only would I not have been in favor of it, President [George W] Bush would not have been in favor of it,” Rubio replied.

Chris Christie, the New Jersey governor who is campaigning without having announced a campaign, took a similar tack on Wednesday.

“I think President [George W] Bush made the best decision he could at the time, given that his intelligence community was telling him that there was WMDs and that there were other threats right there in Iraq,” Christie told CNN.

“But I don’t think you can honestly say that if we knew then that there was no WMDs, that the country should have gone to war.”