Story highlights "He's not a serious adult," Sasse said in the ad

The ad closes with the words: "Unfit. Dangerous. Even for Republicans."

Washington (CNN) A new Hillary Clinton ad is turning to Republicans to make the case that Donald Trump is unfit for the Oval Office.

The ad, titled "Agree," features clips of GOP leaders criticizing the business mogul in interviews and on news programs.

Criticisms come from 2012 Republican presidential nominee Mitt Romney as well as longtime Trump critics such as South Carolina Sen. Lindsey Graham, Nebraska Sen. Ben Sasse and Arizona Sen. Jeff Flake.

"He's not a serious adult," Sasse says in an interview he gave on MSNBC.

The ad closes with the words: "Unfit. Dangerous. Even for Republicans."

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