The fine folks at Pew often compile numbers on what stories people cover, and sometimes they mesh it with what the news has actually covered. For you PhDweeb types, this sounds a lot like agenda-setting, the tired idea that the media do a terrible job of telling people what to think but do a helluva job telling people what to think about.
There's a nice match in this report between what the press covered and what people were interested in. Scroll down and see how media coverage is related to personal interst. The 2008 campaign is first in both, as is the Spitzer story. It's interesting that only 1 percent of coverage forcused on the death of the UNC student (who was from Athens, Ga., my town, a sad story), but 7 percent of Americans were interested. A slight disconnect.
Why does it matter what people think about?
It colors everything. It frames an election. It influences how you consider a candidate, a policy issue. Hell, it affect everything. Political knowledge is one thing, but how a campaign or issue is framed has more persuasive power. The PR folks know this. So do the advertising folks. And the pros who plot political campaigns.
People need to know it too.