1-Democratic Congressional Campaign Committee – $40.6 million

2-National Republican Congressional Committee – $34.5

3-Democratic Senatorial Campaign Committee – $28.9 million

4-American Crossroads – $27.5 million

5-US Chamber of Commerce – $25.5 million

6-American Action Network – $17 million

7-Service Employees International Union – $14.6 million

8-National Republican Senatorial Committee – $13.7 million

9-American Federation of State, County and Municipal Employees – $10.2 million

10-American Future Fund – $8.6 million

Source:  Center for Responsive Politics