John McCain and Barack Obama have both spent time on the presidential campaign trail deriding the amount of money pumped into the political process by special interest groups in Washington, D.C.

But campaigning for any office, and especially for the White House, costs money -- a lot of money.

Below, we've pulled together the top donors to date by industry sector for both Obama and McCain to give a glimpse into how their campaigns are being financed.

We have also tabulated the 2008 top 10 donors to Congress by industry sectors and organization. As you can see, billions of dollars changes hands.

Barack Obama

• Individual contributions: $336,740,735
• PAC contributions: $1,570
• Candidate self-financing: $0
• Federal funds: $0
• Other: $2,474,012

Obama's Top 10 Industry Donors

1. Lawyers/Law Firms: $20,722,629
2. Retired: $19,202,876
3. Securities & Investment: $8,905,777
4. Education: $8,784,068
5. Business Services: $5,875,124
6. Real Estate: $5,816,677
7. Health Professionals: $5,224,639
8. TV/Movies/Music: $4,701,382
9. Misc Business: $3,955,793
10. Computers/Internet: $3,729,991

John McCain

• Individual contributions: $121,232,420
• PAC contributions $1,220,479
• Candidate self-financing $0
• Federal funds $0
• Other $23,013,302

McCain's Top 10 Industry Donors

1. Retired $18,884,993
2. Lawyers/Law Firms $6,874,124
3. Securities & Investment $6,277,757
4. Real Estate $5,795,797
5. Misc Business $3,370,934
6. Misc Finance $3,268,303
7. Health Professionals $2,815,727
8. Business Services $2,165,961
9. Commercial Banks $1,698,978
10. Oil & Gas $1,332,033

Congress: Top 10 Sector Donors 2008

1. Pharmaceuticals/Health Products: $1,439,270,440
2. Insurance: $1,096,146,248
3. Electric Utilities: $985,473,737
4. Computers/Internet: $807,596,171
5. Business Associations: $742,441,001
6. Education: $710,172,651
7. Real Estate: $684,320,914
8. Oil & Gas: $665,862,779
9. Hospitals/Nursing Homes: $636,486,478
10. Misc Manufacturing & Distributing: $601,216,686

Congress: Top 10 Business/Organization Donors 2008

1. US Chamber of Commerce: $28,310,000
2. AARP: $13,700,000
3. Northrop Grumman: $11,633,252
4. American Medical Association: $11,215,000
5. General Electric: $9,600,000
6. American Hospital Association: $9,078,709
7. Verizon Communications: $8,920,000
8. Pharmaceutical Research & Manufacturers of America: $8,630,000
9. Exxon Mobil: $8,130,000
10. Lockheed Martin: $8,015,000

Sources: Center for Responsive Politics, Federal Election Commission, Senate Office of Public Records