"** IRS Makes Database of Political Organizations Available
The Internal Revenue Service has created the
Political Organization Filing and Disclosure Website
At this site you can both file Form 8871, Political
Organization Notice of Section 527 Status, and Form 8872,
Political Organization Report of Contributions and
Expenditures, and search for the same two forms.
The form search interface is available at the Search
Political Organization Disclosures link. There you can
search either form as well as search by organization name,
EIN, or date range.
A search for 'caucus' found 98 results. The results page is
in alphabetical order and includes organization name and
EIN. Click on the name and you'll get an org page with some
basic contact information about the organization as well as
access to their filings. Some orgs I looked at had lots of
filings available (both scanned paper and electronic copies)
while some had only a few. "
this comes from a great site www.researchbuzz.com