Listed below are some basic tools to get started with political opposition research.
Congressional financial disclosures
U.S. House of Representatives financial disclosure reports
U.S. Senate financial disclosure reports,
U.S. House of Representatives gift travel filings
U.S. Senate outside paid travel database
U.S. House of Representatives statement of disbursements (active)
U.S. House of Representatives statement of disbursements (archival)
U.S House of Representatives franked mail/advertisement search
LegiStorm (limited access for free subscribers)
White House records
Federal agency financial disclosures
U.S. Office of Government Ethics ethics documents,
Campaign finance
Federal Election Commission federal campaign finance data
OpenSecrets federal and state campaign finance data
Internal Revenue Service political organization filing and disclosure
Nonprofit records
Internal Revenue Service Tax Exempt Organization Search
ProPublica Nonprofit Explorer
Guidestar Candid
Lobbying
U.S. Senate Lobbying Disclosure Act Reports
OpenSecrets lobbying data,
U.S. Dep’t of Justice Foreign Agent Registration Act filings
Political advertising
Federal Communications Commission Political Inspection Files,
Google Ad Database,
Meta Ad Library,
Federal enforcement databases
Board of Governors of the Federal Reserve System Enforcement actions
Environmental Protection Agency ECHO
Federal Trade Commission Cases and Proceedings,
Occupational Safety and Health Administration Establishment search
Securities and Exchange Commission Enforcement and Litigation
Court records
Corporate records
Cobolt Intelligence Secretary of State Business Search
Good Jobs First Violations Tracker
Vehicle Information
ADS-B Exchange (flight tracker)
Federal Aviation Administration Aircraft Inquiry
VINCheckPro (license plate search)
Google SAR Ship Detection
Online document archives
Freedom of Information Act resources
U.S. Dep’t of Justice FOIA.gov
FOIA Advisor Useful links
National Archives Request Military Service Records
National Archives Official Personnel Folders