Endorser facts

An endorser’s identifiers and size: FEC committee ids, IRS employer id and tax-exemption section, Department of Labor file number and union membership, founding year and parent organization.

Returned by: GET /v1/endorsers, GET /v1/endorsers/{slug}
Found in: Endorser (facts)
Shapes: The full record is in an endorser’s facts. The shorter forms in each fact leave some fields out; a field that isn’t in every form says where it is.

How it connects

On every endorser as facts; with format=csv, GET /v1/endorsers has each as a column.
fec_committee_ids join FEC data (contributions, independent expenditures); ein joins IRS filings; olms_file_number joins Department of Labor reports.

Good to know

Each fact is taken from the body responsible for it: the FEC committee master files, the IRS Exempt Organizations Business Master File, the Department of Labor’s union annual reports (all U.S. government works), or the endorser’s own About page for founded_year and parent_organization. Endorsers were matched to those files by name and, for an endorser with a home state, by state; an endorser that matched more than one record was left without one.
union_members is what the union itself reported to the Department of Labor, for the period ending union_members_as_of; sources keeps earlier years too.
No contributor, officer or treasurer names are kept.

Fields

Field	Type	Meaning	Example
`fec_committee_ids`	array of string	Federal Election Commission committee ids (C########) of the endorser’s political committees, from the FEC committee master files 2020-2026. Empty where we found none.Only in an endorser’s facts.	—
`ein`	stringor null	IRS employer identification number, nine digits.Only in an endorser’s facts.	`951310931`
`irs_subsection`	stringor null	The tax-exemption section the IRS lists, such as 501(c)(4) or 501(c)(5).Only in an endorser’s facts.	`501(c)(5)`
`union_members`	integeror null	Members the union reported on its latest Department of Labor annual report (LM-2, LM-3 or LM-4).Only in an endorser’s facts.	`25542`
`union_members_as_of`	stringor nullYYYY-MM-DD	The end of the report period union_members is for.Only in an endorser’s facts.	`2025-12-31`
`olms_file_number`	stringor null	The union’s Department of Labor (OLMS) file number.Only in an endorser’s facts.	`7156`
`founded_year`	integeror null	The year the organization says it was founded.Only in an endorser’s facts.	—
`parent_organization`	stringor null	The organization it says it is an affiliate or chapter of.Only in an endorser’s facts.	—
`sources`	array of Endorser facts	Every fact above, each with its source and date; older union member counts too.Only in an endorser’s facts.	—
`fact`	string	Which fact.`fec_committee_id`, `ein`, `irs_subsection`, `union_members`, `olms_file_number`, `founded_year`, `parent_organization` meaningsOnly in each fact.	`ein`
`value`	string	The value as the source gives it.Only in each fact.	`951310931`
`as_of`	stringYYYY-MM-DD	The date the fact was true per its source: the end of the report period for union members, the IRS file’s posting date, or the day we read the file or page.Only in each fact.	`2026-11-10`
`source`	object	The source of the fact.Only in each fact.	—
`source.name`	string	Who published the fact.Only in each fact.	`IRS Exempt Organizations Business Master File extract`
`source.url`	stringURL	Where the fact was published.Only in each fact.	`https://apps.irs.gov/app/eos/details/?ein=951310931`
`retrieved_on`	stringYYYY-MM-DD	When we read it from the source.Only in each fact.	`2026-11-14`

Download every dictionary as CSV or JSON.

Sample (JSON)

One endorser facts as the API returns it, in an endorser’s facts. More in the sample data.

{
  "fec_committee_ids": [],
  "ein": "951310931",
  "irs_subsection": "501(c)(5)",
  "union_members": 25542,
  "union_members_as_of": "2025-12-31",
  "olms_file_number": "7156",
  "founded_year": null,
  "parent_organization": null,
  "sources": [
    {
      "fact": "ein",
      "value": "951310931",
      "as_of": "2026-11-10",
      "source": {
        "name": "IRS Exempt Organizations Business Master File extract",
        "url": "https://apps.irs.gov/app/eos/details/?ein=951310931"
      },
      "retrieved_on": "2026-11-14"
    },
    {
      "fact": "irs_subsection",
      "value": "501(c)(5)",
      "as_of": "2026-11-10",
      "source": {
        "name": "IRS Exempt Organizations Business Master File extract",
        "url": "https://apps.irs.gov/app/eos/details/?ein=951310931"
      },
      "retrieved_on": "2026-11-14"
    },
    {
      "fact": "olms_file_number",
      "value": "7156",
      "as_of": "2025-12-31",
      "source": {
        "name": "DOL OLMS LM-2 annual report",
        "url": "https://olmsapps.dol.gov/query/orgReport.do?rptId=935167&rptForm=LM2Form"
      },
      "retrieved_on": "2026-11-14"
    },
    {
      "fact": "union_members",
      "value": "25542",
      "as_of": "2025-12-31",
      "source": {
        "name": "DOL OLMS LM-2 annual report",
        "url": "https://olmsapps.dol.gov/query/orgReport.do?rptId=935167&rptForm=LM2Form"
      },
      "retrieved_on": "2026-11-14"
    }
  ]
}