I think the media defintely influences the general public's desire to be involved in the political process. Whether they will admit it or not, most news organziations have either a liberal or a conservative slant to their reporting. How news is conveyed to the audience can anger or appease the voters toward or against individual candidates.
For example, if a reporter portrays a candidate as a liar, or an idiot...people will likely believe the news report instead of doing independent research...and they will vote against the politician being smeared.
I lived in Iowa for 12 years and was continually inundated with political news and information; in fact, it seemed as if the election cycle never really ended. Just as one vote happened, the next batch of candidates and issues moved to the forefront. When so many candidates (and potential candidates) are vying for attention, the media has the power to help or hurt their cause by the amount of coverage each is given as well as the perspective from which the news is told. Laws exist to help maintain equal time in formal settings; but the informal coverage is a powerful tool of persuasion. The more a candidate is seen, the more recognizable he or she is--and candidates all covet that kind of name recognition. The media has the ability to shift the flow of an election, at least to some degree, as it chooses who and how to cover the candidates. Perhaps this is less true once the field is more limited, but in the earliest days of an election cycle, the media has tremendous power.
The media has many different roles when it comes to political involvement. The media helps to evaluate the credentials of a given candidate and categorize their political views and proposed policies. This aspect of the media's role seems to be somewhat beneficial. However, the media can also pigeon-hole a candidate and portray them in a distorted fashion as well as exaggerate unimportant issues such as petty feuds between candidates. This aspect seems to be detrimental.
I would argue that media coverage of politics can actually work to reduce political participation. The media tends to focus on the most contentious and sordid aspects of our political system. By doing this, they make us feel that our politicians are incredibly selfish and petty people. This makes it much less likely that we will want to participate because we have so little respect remaining for the political process and the politicians.
In my opinion, the right-wing media make a significant contribution to polarization, with inflammatory language, inaccuracies, sometimes deliberate, and information presented completely out of context. This manipulation influences peoples' thinking and has a direct impact on the political process by causing voters to make choices they would not otherwise make. Perhaps journalism never was the honorable profession I believed it to be, and I am just an old fogey, but it seems to me that there are media outlets today that do not even pretend to adhere to a code of ethical journalism.
Of course, the term "media" has expanded for many people to include forms such as blogging and tweeting, and I am afraid there are people who cannot make a distinction between a reputable news source and this sort of thing. There clearly is no code of ethics for much of what passes for media today.
In the present day and age, voters know more about candidates, their stands on issues, even their personal lives because of the media. The above posts cite incidences of persuasion by use of media; however the far greater effect is that of the news media. Newspapers, television reports, even tweets and facebook postings all inform voters of candidates' activities and positions on important matters. This was not the case in the not too distant past.
Another example of the media getting involved in political matters is the Rock the Vote campaign. The tying of music, something all young people listen to, to a political matter, getting out and voting, allowed young persons to feel as if they were a true part of the movement.
One specific example of media and the influence on the political participation is to consider the "get out the vote" campaigns that have been run on television programming such as MTV -- channels that traditionally draw a young audience. By talking directly to young people about exercising their to vote and the power of their vote, young people went to the polls in much greater numbers than they had in previous elections. When you also consider campaigns used social networking such as Twitter and Facebook it is no wonder that young people have become more politically active.