Story highlights The ad -- hitting Bush on his comments about his brother, former President George W. Bush, will begin airing nationally on cable news stations next week

"As it relates to my brother, there's one thing I know for sure: He kept us safe," Bush said Wednesday

Washington (CNN) A progressive group is invoking the Sept. 11 terror attacks to hit Jeb Bush for comments he made about his brother at Wednesday's CNN debate, when he said President George W. Bush kept the country "safe."

Jeb Bush's comments were in response to a line of attack from Donald Trump about his brother's presidency, which the billionaire businessman labeled a "disaster."

"As it relates to my brother, there's one thing I know for sure: He kept us safe," Bush interjected, to roaring applause from the audience. It was one of his top moments of the night.

But the liberal-aligned Americans United for Change is seizing on those comments with their ad , titled "Safe?"

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