In October 2016 James Scott, a Senior Fellow at the Institute for Critical Infrastruction Technology, joined a panel of experts in a discussion on cybersecurity threats. During the panel James and the other experts highlighted vulnerabilities of the U.S. election system and specified ways adversaries can compromise voting machines and data.
James Scott told the panel the easiest way to compromise the US election system was during the manufacturing process.
Then entire panel was broadcast on CSPAN.
Here is a clip via M3THODS.