In our democratic system candidates need to get elected by the people. To get votes the voters need to know who you are and what you are running for. If you aren't able to get your name heard by enough people you will not be able to get elected. In order to make everyone know who you are, your name needs to be in the media. Obviously, to get your name out there in the form of advertisements you need money, and lots of it. Without lots of money it is impossible to create enough publicity for yourself to get elected. Many people argue that this is the biggest drawback to the democratic system since it favors those with lots of money over a candidate who may not have as much money to spend campaigning.
Candidates know that it takes quite a bit of money to run for office and they are constantly looking for ways to get it. Candidates can get money for a campaign from many sources. Wealthy individuals, corporations, unions, political action committees, and party committees all frequently contribute to the campaigns of those candidates that they would like to see in office. If a candidate favors issues that coincide with the feelings and beliefs of any particular special interest group, that group will usually support the candidate with contributions to their campaign. They make these contributions to help ensure that a candidate will get elected over a candidate who may not agree with a certain group's point of view. For example, an environmental group may make large contributions to the campaign of a candidate who supports protecting the environment.
Our country has realized that we can't just let someone spend their way into political office and that we need to have campaign finance reform. In 1883 the Pendleton Act was the first significant attempt to reduce the influence of money on politics. It said that "Federal workers are under no obligation to contribute to any political fund, or to render any political serv