"She'd make a tremendous president," Petraeus says in the new book "HRC" by Jonathan Allen and Aimee Parnes.
And for Petraeus, Exhibit A in why she would be a tremendous president is the very thing for which Republicans most aggressively attack Clinton: her performance as Secretary of State when the U.S. consulate in Benghazi, Libya, was attacked.
"Like a lot of great leaders, her most impressive qualities were most visible during tough times," Petraeus tells Allen and Parnes. "In the wake of the Benghazi attacks, for example, she was extraordinarily resolute, determined, and controlled."