Jeb Bush got thunderous applause from the Republican audience at last week's presidential primary debate when he said his brother, former President George W. Bush, "kept us safe."

But he's about to get something very different from a liberal outside group called Americans United for Change: An ad reminding him that his brother was president during the Sept. 11, 2001 terrorist attack on the US, the American invasion of Iraq, the failed federal response to Hurricane Katrina and the 2008 financial crisis.

Many Democrats believe that the party was too pliant for the elder Bush brother in the wake of the terrorist assault, ceding important ground on both policy and politics. The ad from AUC, which shares its president with the Hillary Clinton-backing superPAC Correct the Record, is an indication that the Bush family narrative about the national security bona fides of George W. Bush won't go unchallenged.

"It’s as if Jeb Bush believes his brother’s presidency began on September 12th, 2001. But we’re not letting Jeb rewrite history," Brad Woodhouse, the president of AUC, said. "It’s convenient but not honest to ignore the facts that the worst attack on American soil since Pearl Harbor happened on George W. Bush’s watch after dismissing warnings from U.S. intelligence officials weeks before 9/11 that Osama bin Laden was ‘determined to strike in US’ and that his terrorist network might hijack American planes."

Vox's Matt Yglesias made a similar point right after the debate.

The Bush campaign did not immediately respond to Vox's request for comment. But Bush spokesman Tim Miller pushed back on AUC and Clinton for a story on the Tampa Bay Times website.

"Hillary Clinton's political machine resorting to attacking Jeb over 9/11 is a depressing example of just how extreme the left has gotten," Miller said. "If there's one thing we should all agree on its that in response to that horrific attack, the country came together with resolve in the face of evil to ensure we keep our country safe. Today, while Jeb has offered a plan to defeat ISIS the Democrats have no strategy so they are left to make these craven attacks."

AUC says the ad will start running Monday on cable television across the nation. Whether or not it's effective in convincing voters that Jeb Bush is wrong about his brother, the ad suggests Democrats have more of a stomach for challenging the Bushes on national security than they did 10 or 15 years ago.

Correction: Woodhouse is president of Americans United for Change and Correct the Record.