Republican presidential hopeful Jeb Bush responded Sunday night to a new television ad targeting his brother George W. Bush’s presidency, terming the commercial "disgraceful." In a Twitter post, Jeb Bush suggested that Democratic presidential candidate Hillary Clinton's "political machine" was behind the 30-second ad.

The ad, which is scheduled to air this week, was released online Saturday by Americans United for Change, a progressive group that reportedly has close ties with Clinton. It was apparently aimed at Jeb Bush’s comments during last week’s presidential debate, in which he defended George W. Bush’s national security policy saying that the former president "kept us safe."

The ad features Jeb Bush’s debate comments mixed with clips of some of the events during George W. Bush's presidency such as the war in Iraq, the Sept. 11 terrorist attacks and the reaction to Hurricane Katrina. The ad suggests that the 69-year-old did not keep Americans safe from "a crumbling economy," "a bureaucratic catastrophe" and "an unnecessary war."

“As it relates to my brother, there’s one thing I know for sure: He kept us safe,” Jeb Bush said Wednesday, in response to Donald Trump’s comments that Bush’s presidency was a disaster.

Brad Woodhouse, president of Americans United for Change, said in a statement Saturday: "It’s as if Jeb Bush believes his brother’s presidency began on September 12th, 2001. But we’re not letting Jeb rewrite history.

"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."

Jen Bush's Twitter post Thursday of a photo of George W. Bush atop a pile of World Trade Center rubble, along with his comments from the GOP debate, had received criticism on social media, despite his remarks being applauded during Wednesday night's Republican presidential debate.