The nonpartisan, nonprofit National Institute on Money in Politics (NIMP) promotes an accountable democracy by compiling comprehensive campaign-donor, lobbyist, and other information from government disclosure agencies nationwide and making it freely available at FollowTheMoney.org.
The Institute researches and archives a 50-state federal/state database of contributions documenting $100+ billion, plus more than 2 million state lobbyist-client relationships that are registered annually. Recent expansions include selected local-level data, collecting independent spending reports for federal campaigns and in 31 states, and lobbying spending in 20 states.
Has a REST API: https://www.followthemoney.org/our-data/apis
You have to register for a free API key to use it. By default, you can pull up to 1000 records per year.
How to find your API key:
- Log in.
- Scroll down to Data Export.
- Click JSON.
- A modal will pop up with a link that contains, among other things, your API key.
- Click the link.
- Grab your API key out of the URL.