Identifying TV Political and Issue Ad Sponsors in the Digital Age [September 9, 2020] [open pdf - 1MB]
From the Summary: "Since the 1930s, both Congress and the Federal Communications Commission (FCC) have imposed specific requirements on the transmission of political and issue advertising by broadcasters. These rules, which now apply to broadcast radio and television stations, cable and satellite television distributors, and satellite radio services, mandate that the sponsors of political and issue ads be clearly identified within each announcement and that media organizations maintain files of political advertisers' requests for advertising time and make those files available for public inspection."
CRS Report for Congress, R46516
Congressional Research Service: https://crsreports.congress.gov/