According to letsfreecongress.com, in the 2012 US House elections, 95% of the candidates that outspent their opponents won, and 1% of the donors contributed 68% of the campaign funding.
In 2010, spending by Charles and David Koch’s Americans for Prosperity unseated Democrats Eric Oemig and Randy Gordon from the Washington State Senate in the 41st and 45th LD, replacing them with Republicans Steve Litzow and Andy Hill. (The State Republican Party was later fined for violating election reporting requirements in that election. See also How the Koch Brothers worked to defeat Democrats in Washington State.) Litzow beat Gordon by about 200 votes, because of last minute attack ads.
The Washington State Public Disclosure Commission lists contributions to Litzow’s campaign. Contributions include, among others,
ACLI (American Council of Life Insurers) POLITICAL ACTIVITY FUND: $1000.
ALLSTATE INSURANCE CO $1000
AMERICAN CHEMISTRY COUNCIL $950
AMERICAN INSURANCE ASSOCIATION $1000 x 2
ASSOCIATED GENERAL CONTRACTORS BUILD PAC $950 x 2
ASSOCIATION OF WASHINGTON BUSINESS $1000
AVISTA CORP (energy) $1000
BNSF RAILWAY COMPANY $1000 x 2
BOEING PAC $900 x 2
BOMA PAC OF WASHINGTON (Building Owners and Managers): $1000
BP NORTH AMERICAN $900
CAMBIA (health) $1000
INSURANCE AND FINANCIAL ADVISORS PAC $1000 x 2
WEYERHAEUSER GEORGE H $1000
Connie and Seven Ballmer: $1000 each, as did Jacklyn and Miguel Bezos.
Click here to see the full list.