The media can influence campaigning in a number of ways. One example would be that the media can take the time, and has the resources, to do fact checking. This is important because the average voter does not or is not able to verify the statements that are used in a campaign. This influence can be minor (such as a statement taken out of context) or it can be devestating (such as uncovering corruption or misconduct). In any event, the campaign must adjust its strategy to compensate for the reporting and subsequent public response.
In the same way that the media's fact checking can have a negative impact on a compaign, it can also have a positive effect. One example of this would be if a candiate's statements were proven to accurate or if past honors or awards are broadly reported (by doing this, the media provides a campaign free advertising as well as independent verification).
Another possibility is that the media can influence an election by not reporting on it or not providing equal time or access to all campaigns. This is especially true in regards to independent or small party campaigns since they are normally overlooked and, as such, voters are not aware of their positions compared to the more main-stream candidates.
One opinion is that campaigns should not be subjected to spending limits. The reason for this is that citizens should have the right to spend their money in any way they see fit. It can be argued that this is an extension of free speech which is protected by the 1st admendment.
