Former president George H.W. Bush, left, then-President George W. Bush and then-Florida Gov. Jeb Bush at Cape Arundel Golf Club in Maine in July 2001. (Kevin Lamarque/Reuters)

He didn’t plan to say it. But two hours into the second Republican presidential debate, Jeb Bush took a firm stand.

“He kept us safe,” he said.

The quick and simple defense of his brother George W. Bush earned one of the loudest rounds of applause of the night. Aides said it was an impromptu decision spurred by an attack from Donald Trump, the GOP front-runner.

But those four words refocused a campaign in desperate need of a “moment,” and they signaled the extent to which Jeb Bush has become comfortable — even eager — about highlighting rather than playing down his family ties.

Those four words also ignited a broader debate about George W. Bush’s legacy and whether the former president kept the nation safe during his eight years in office, which included the attacks of Sept. 11, 2001, and the beginning of a war in Iraq that is still reverberating a dozen years later.

During the second GOP debate, Republican presidential candidates Donald Trump and Jeb Bush clashed on former president George W. Bush's response to terror threats following the 9/11 attacks. (CNN)

Among Republicans, the 43rd president is more popular now than at any point since leaving office, but Americans overall still have mixed feelings about him. That’s why Democrats — and some of his Republican rivals — seized on Jeb Bush’s debate comments as evidence of a candidate blindly loyal to a family member still reviled by many voters.

“We’re not going to let Jeb Bush rewrite history,” said Brad Woodhouse, head of Americans United for Change, a Democratic group that is airing television ads criticizing the Bush brothers. “If Jeb Bush really believes his brother kept us safe, how can the American people entrust their safety to Jeb Bush?”

Republicans are torn on whether a firmer embrace of the family history will help.

Fergus Cullen, former chairman of the New Hampshire Republican Party, warned recently that “Bush fatigue is real,” adding: “I don’t think it’s something that he can’t overcome, but I definitely think there are a lot of Republicans who are interested in Jeb Bush and like what they’ve seen and heard but have reservations about whether or not the country is ready to elect another Bush.”

Ron Bonjean, an unaligned GOP strategist, said that “it’s a razor’s edge of embracing his brother because of family loyalty and creating his own path, which Jeb Bush must do to show his independence. However, Bush would turn off conservative voters if it looked like he was disavowing his family for the sake of political gamesmanship.”

All year, Bush has been locked in a constant push and pull with his famous family, whose political service spans four generations.

George W. Bush and Jeb Bush with their mother, Barbara Bush, in Midland, Tex., in 1956. (George Bush Presidential Library and Museum)

During a speech in February before the Detroit Economic Club, he was asked what effect his famous last name might have on his decision to run.

“I’ve had a front-row seat to kind of watch history unfold, a unique seat. It’s given me some perspectives that are helpful,” he said.

Last Friday, again speaking in Michigan, he echoed those earlier comments by suggesting that he is uniquely qualified to restore the country’s international relations.

“I know how to do this because, yes, I am a Bush,” he told the crowd. “I happened to see two really good presidents develop relationships with other countries.”

The crowd at the Mackinac Republican Leadership Conference — a gathering of major GOP donors — gave him a big round of applause.

The day after the debate, the Bush campaign tweeted out a picture of George W. Bush standing on the rubble of the World Trade Center alongside a New York firefighter. The image was accompanied by Jeb Bush’s assertion that his brother “kept us safe.”

Aides said that crowds should expect to hear similarly straightforward defenses from Bush about his family.

“Given how strong of a contrast it was with Trump on the debate stage, it makes sense to follow up on what was a good moment,” said Tim Miller, Bush’s campaign communications director.

That’s a departure from how Bush has handled his family before. In March, he introduced himself to voters in Iowa as “George’s boy and W’s brother,” referring to his father, former president George H.W. Bush, before quickly pivoting to share his own history.

“All of my mistakes I made in my life are my own doing; they have nothing to do with my family,” he said. “I have a great family. But I’ve been on my own journey.”

Polling is somewhat conflicted on George W. Bush, but his image has improved a great deal since he left office in 2009. Americans still generally disapprove of his performance, but Republicans see him positively.

He left office with a 37 percent favorability rating; 62 percent of Americans viewed him unfavorably, according to a January 2009 Washington Post-ABC News poll. His job approval rating stood at 33 percent.

But in May, a CNN-ORC poll gave George W. Bush a 52 percent favorability rating — the best of his post-presidency to date. Republicans in the poll had an overwhelmingly positive view of Bush, 88 percent favorable, compared with 7 percent unfavorable.

Jeb Bush has a foreign-policy kitchen cabinet packed with 21 members of his father’s and brother’s administrations. The team includes former secretary of state James Baker, despised by neoconservatives, and Paul Wolfowitz, a former deputy defense secretary reviled by many critics of the second Iraq war.

Bush told the Chicago Council on Global Affairs in February that “there were mistakes in Iraq for sure.” But he also said the 2007 troop “surge” ordered by his brother “was one of the most heroic acts of courage politically that any president’s done.”

In the months since, Bush has bristled at war critics or at questions about why he’s relying so heavily on his brother’s advisers.

“If they’ve had any executive experience, they’ve had to deal with two Republican administrations,” he told a voter who asked him about his team while visiting the Iowa State Fair in August. “Who were the people who were presidents, the last two Republicans? I mean, this is kind of a tough game to be playing, to be honest with you. I’m my own person.”

He gave a similar answer when asked about ties to former Bush administration aides during last week’s debate.

In March, a 19-year-old college student confronted Bush about his belief that the Islamic State has been an outgrowth of the Obama administration’s decision to withdraw U.S. military forces from Iraq. Ivy Ziedrich argued that it was George W. Bush’s decision to begin the Iraq war that laid the groundwork for the terrorist group.

“We respectfully disagree,” Bush told Ziedrich, adding later: “You can rewrite history all you want, but the simple fact is that we’re in a much more unstable place because America pulled back.”

In the debate last week, George W. Bush earned the ire of Trump, who said the former president had been “such a disaster” that it led to the election of Barack Obama. When Jeb Bush defended his brother, Trump retorted: “I don’t know. You feel safe right now? I don’t feel so safe.”

Sen. Rand Paul (R-Ky.) has also been critical of George W. Bush’s oversight of the Iraq war and of his decision to expand surveillance powers in the wake of the 9/11 attacks. Other GOP candidates, however, jumped to the former president’s defense, including New Jersey Gov. Chris Christie, who was appointed a U.S. attorney by George W. Bush.

The ad from Americans United for Change begins with footage of Jeb Bush in the debate defending his brother. On screen, the ad asks viewers whether George W. Bush kept the country safe from “a crumbling economy,” “a bureaucratic catastrophe” in response to Hurricane Katrina and “an unnecessary war.” The examples end with footage of the 9/11 tribute lights at Ground Zero and the words “SAFE from terror?”

The Bush campaign dismissed the ad as “a depressing example of just how extreme the left has become.” An e-mail to Bush supporters warned that Democratic presidential candidate Hillary Rodham Clinton’s “political machine is preparing to spend hundreds of thousands of dollars on a new TV ad attacking Jeb and his brother over September 11, 2001.”

“We expected attacks, but we didn’t think the Democrats would stoop this low with outrageous, disgraceful ad buys,” the e-mail said.

Americans United for Change is a Democratic group founded during George W. Bush’s administration and has no formal ties to the Clinton campaign.

Until recently, George W. Bush had avoided engaging in campaign politics — privately warning his brother and top-flight GOP donors that he would quickly become a political liability. But George W. Bush headlined a fundraiser in New York this month, and he has other upcoming fundraising dates scheduled in Texas, Arkansas, Colorado and Washington, D.C. The brothers also will appear together at a conference for major campaign donors in late October, alongside their father.

George H.W. Bush appears to be less of a worry: Americans view the 41st president favorably by a margin of about 2 to 1, according to an CNN-ORC poll from May.

“My dad is the greatest man alive in my mind,” Jeb Bush said in May. “I have to admit, I’m not particularly objective about the subject, so if someone wants to argue with me I’ll take you outside and get beat up.”

That line proved so popular with some voters that the Bush campaign put the quote on a T-shirt available for purchase on his campaign Web site. Nothing for sale on the site references George W. Bush — at least not yet.

Sean Sullivan in Mackinac Island, Mich., and Scott Clement in Washington contributed to this report.