The main cause of corruption in India are the politicians. They are the ones who need money to fight an election. 
Approx; 35 to 50 lakhs are needed by a politician to fight MEMBER OF PARLIAMENT (MP) election, 10 to 20 lakhs to fight MLA election and around 3 to 5 lakhs for fighting municipal councilor election. The total black money required for a 5 year term for all the election is about 2500 Crores plus their daily requirements. 

Following are the places from where the black money is generated:

1. Defence Deal by Central Government.

2. Oil Import/ Telecom Licenses/ Sugar import/ Purchase of Aircraft by Civil Aviation Department/ Doordarshan/Chemicals & Fertilizers/Urea Import or Exports/ ISP Licenses/ Foreign Direct Investment Proposals/Giving Licenses for Oil Drilling Operation/ Power Generation/ Railways/ Steel Import or Export licenses/Textile Policy/ Drug Policy etc.

3. Disinvestments of Public Sector Undertakings.

4. Transfer of officers in Income Tax/ Police Personals/Banking Sector/Public Sector/Foreign Postings etc.

1. Disclosure of Income and other details by Politicians before election
Public disclosure by candidates will certainly help in encouraging transparency and probity; when data is made public, it is possible for the candidate's competitors, the media and other public interest groups to probe and challenge any information they suspect. And, moreover, access to such information by the public is bound to make political parties more careful in their choice of candidates.

It will also help the voter in exercising a certain degree of political maturity in voicing their mandate by paying more attention to the credibility of the candidates, their leadership potential and priorities. The first effort taken in this direction proves that promoting transparency in public life is certainly feasible. We are highly enthused by the positive response showed by the candidates themselves. Perhaps the time has come for the authorities concerned to mandatory requirement that all candidates have to furnish a basic set of information while registering nominations; the precise nature of the information has to be worked out. Given the clamour for transparency and openness, it is high time that the voters get to know their candidates beyond the image provided by cutouts, handouts and megaphones.