The Pew study concluded that although many Americans do still get their political news from mainstream media sources (both online and through TV and newspapers), more and more voters are choosing to use the internet to find out more about the potential candidates. This would certainly help the case of "underdog" candidate Ron Paul, who thus far seems to be winning the election on the internet.
I'm sure part of the reason that people are turning to the internet is due to the mainstream media's refusal to actually cover candidates in depth. Part of that is most certainly due to the vast majority of the candidate's lack of depth but also due to other factors such as government pressure, bias and entertainment value. In spite of the fact that news is a big part of the media's budget, politics is boring to most viewers.
Those who are interested in politics will not find satisfaction from mainstream outlets by and large.