The state reports will usually be filed with the Secretary of State's office in each state capitol. For both federal and state election reports, remember how busy election time is for the agencies that receive and process the reports. If you make a document production request around election time, give the agency plenty of lead time. The campaign finance reports will list major donations, expenditures, and will also list some of the major campaign officers. Guides to Congress, such as the Almanac of American Politics, Congressional Directory, and Congressional Quarterly Politics in America all have biographies of Congresspersons.
Many state legislatures publish low-cost booklets giving short biographies of the members.
Your town library may also have back issues of the local newspaper on microfilm or microfiche, plus an index to the old newspaper articles. Biographical articles about the legislator will be a strong source of information, and may tell you who his political allies are. Computer databases such as Prodigy, Compuserve, and Nexis may also be useful. These databases usually contain a specialized political biography library. Even better, they also contain full-text versions of newspaper articles, allowing you to pull up dozens or hundreds of articles dealing with every facet of the legislator's career.