Information displayed by ProPublica’s Election DataBot comes from multiple sources, including government and commercial websites:
Information about campaign filings comes from the ProPublica Campaign Finance API, which retrieves data from the Federal Election Commission. Specifically, House and Presidential candidates file electronic campaign reports that are updated every 15 minutes. Senate candidates file reports on paper that are posted to the FEC’s site and are retrieved once a day.
Information about how incumbents vote comes from the ProPublica Congress API, which retrieves data from official House and Senate websites. We limit what we surface in Election DataBot to two events: whether a vote is cast against a majority of a lawmaker’s party, or is the only “Yes” or “No” vote on a bill. Not all votes are displayed, just significant procedural votes or on-passage votes. While votes typically are published within an hour of taking place, amendment votes in the House may not appear until after all votes are finished for the day.
Hourly data on search interest for individual candidates is provided by Google Trends, which tracks search volume. All presidential candidates and most congressional candidates have unique identifiers used to retrieve the data. Trends data is not comprehensive, but represents a sample of Google searches.
Demographic data for congressional districts is from the Census Bureau. For most states, the data is from the 2014 American Community Survey 1-year survey. For Florida, North Carolina and Virginia districts, which were redrawn in the past year, the data is from the 2010 Census and reflects the new boundaries. For Virginia, race and ethnicity percentages exceed 100 percent because white and black populations also include those with Hispanic ethnicity.
Changes in race ratings for Senate and House races are from the Cook Political Report, which provides non-partisan analysis of elections. They are updated once daily.
Win probabilities for the presidential race in every state are provided by FiveThirtyEight, which updates its forecasts as new polls are released. The Election DataBot uses the “polls-only” forecast, which is based on an analysis of polling data.