By 1980, but probably much further back than that going back to 1968 or 64 TV and TV news especially was already a huge factor in how Americans got their political news and other current affairs news. Because even by 1980 ABC News, NBC News and CBS News broadcast news was the really the only game in town when it came to TV broadcast news coverage from. There was radio, but most Americans got their radio news in the car and not so much at home except when they are getting ready to go to bed or getting ready for work in the morning.
CNN was the only cable news network on TV and they were just getting started in 1980 and C-SPAN again had just gotten started and them along with CNN probably had about the same amount of viewers as PBS. This was way before the whole menu of cable news networks and so-called news networks like FNC, MSNBC and RT. This was also pre-internet, so of course there were no blogs and as a result the print publishing business was in much better shape with newsmagazines and newspapers. So broadcast TV news was the leader at this point in how Americans got their news.