I recall Evan Thomas, editor of Newsweek, claiming in the late 1990's or early 2000's that the effect of the media was worth 10-15% in the polls. (Did you know that he was the grandson of Norman Thomas, BTW? It figures. See also, this afternoon's post about the parents and grandparents of public figures, The Right Sort.) It was an overestimate even then - it would have been correct for 1990 - but was interesting in that it was one of the few admissions from the lodge that is the legacy media that they do influence the vote. I had maintained for years that without that advantage the Democratic Party would have ceased to be viable and would have had to change to survive. (Helloooo, James Webb for VP.)
There had been a lot of conservative insisting in the previous decade that the dominant media displayed significant bias, despite their claims of fairness. There was a lot of handwringing in the opposite direction, deploring how much influence Drudge Report and talk radio were having, because those weren't objective news sources and people were being INFLUENCED by them. When Fox* News came on board in 1997 the long knives were immediately out.
Jonah Goldberg at National Review had a response to the complaints about the growth of conservative media that I think still holds. I am paraphrasing from memory: Well, then, let's trade. Conservatives get the NY Times, the Washington Post, Chicago Tribune and most of the other newspapers, plus the AP and UPI. We'll take over ABC, CBS, NBC, CNN, and PBS. You turn over Hollywood and academia to us, and the major publishing houses, including the textbooks. Wait, I'm not finished. You give us Time, Newsweek, all the women's magazines, plus most of the political magazines. In return you can have talk radio, the Wall Street Journal (usually), Drudge Report, Fox News, Weekly Standard, and National Review. Deal?
The territory is different now, and the internet has definitely allowed the many types of conservatives and libertarians to get their word out more. Newsweek and Time are gone. Yet I still think that the idea behind that trade should occur to us when there is wailing about the influence of conservative media, as if this is some sort of fifty-fifty deal where both sides have to try and improve and be a little fairer. Liberals control great swaths of the media still. How much influence do they have? I think it is still great. I no longer have a good intuitive sense, as I follow it all less and less. But I still think the Democratic Party would not survive without their assistance.
*I have never seen Fox News, BTW, except some linked clips, some of them trying to show it in a positive light, some in a negative. Oh, and the unedited feed you can get on a cruise ship. I watched a few minutes of MSNBC, also. I've heard a lot about them, but that's not the same. My videographer son tells me their production values are less good than other networks.