HKS Lecturer Juliette Kayyem, a national security expert and author of “Security Mom,” digs into the “Goldilocks” problem of security in the United States, analyzing whether the Transportation Safety Administration (TSA) is worth the cost and hassle to air travellers; providing historical context to US approaches to safety and security; and explaining why national security is shaping up to become the central theme in the 2016 presidential general election, and what that means for the candidates.