Why do people spend money on elections?

My campaign is about the "money monster" in politics and how to tackle that monster without abridging the right of free speech.

This week's Supreme Court decision  in the McCutcheon case involved our own Alabama businessman Shaun McCutcheon.  In the syllabus of the Supreme Court McCutcheon decision, the facts were stated that:

In the 2011–2012 election cycle, appellant McCutcheon contributed to 16 different federal candidates, complying with the base limits applicable to each. He alleges that the aggregate limits prevented him from contributing to 12 additional candidates and to a number of noncandidate political committees. He also alleges that he wishes to make similar contributions in the future, all within the base limits.

The decision in the McCutcheon case prompted the national news networks to do "money in politics" stories, featuring, among others, the Koch brothers, and it all got me wondering about what the reasons are people spend money on elections.

I found this article to be informative, but don't know how much more there is to the story: Koch brothers plan big for 2014 – but what do Charles and David really want?

The website of OpenSecrets says

Our Mission: Inform, Empower & Advocate
The Center for Responsive Politics is the nation's premier research group tracking money in U.S. politics and its effect on elections and public policy. Nonpartisan, independent and nonprofit, the organization aims to create a more educated voter, an involved citizenry and a more transparent and responsive government.
In short, the Center's mission is to:

• Inform citizens about how money in politics affects their lives

• Empower voters and activists by providing unbiased information

• Advocate for a transparent and responsive government

We pursue our mission largely through our award-winning website, OpenSecrets.org, which is the most comprehensive resource for federal campaign contributions, lobbying data and analysis available anywhere. And for other organizations and news media, the Center's exclusive data powers their online features tracking money in politics - counting cash to make change.
The Center relies on financial support from a combination of foundation grants, individual contributions and income earned from custom research and licensing data for commercial use. The Center accepts no contributions from businesses, labor unions or trade associations. You can support the work of the Center directly by making a tax-deductible contribution through OpenSecrets.org.

Fundraising in the Alabama 6th Congressional district

This January 21st article reports that the fundraising for the first period ended December 31, 2013 shows the following amounts.

Brooke  $320,000

DeMarco  $360,000

Mathis  $350,000

Palmer  $250,000