What are the trends in voter registration by party in Illinois since 2020?
Executive summary
Illinois does not collect or report voters’ party affiliation at registration, so there are no official state-level trends in “voter registration by party” for 2020–2025; the State Board of Elections publishes registration totals but not party breakdowns [1] [2]. Analysts and third parties infer partisan trends from voting history, party lists, and private datasets, but those are estimates rather than official registration-by-party counts [3] [4].
1. Illinois’ baseline rule: no party on the registration form
Illinois law and county election offices state plainly that the state “does not have a political party registration system,” meaning registrants do not declare a formal party when they register to vote. That single fact is the crucial limiter: the state’s public registration database provides counts of registered voters but not party labels [1] [5]. The Illinois State Board of Elections’ registration pages reiterate that candidate and turnout data are available while registration counts are “unofficial” and updated frequently, but they do not supply partisan tallies [2].
2. What official sources do provide: raw registration totals and voter history
The State Board of Elections and county sites publish total registered-voter counts and voting history for particular elections; those numbers show how many people are registered and how many voted, including in 2020’s record turnout, but they stop short of tying individual records to party affiliation at registration [2] [6] [7]. For example, post‑2020 coverage noted large increases in registration and record turnout — reporting a rise of about 234,252 registered Illinoisans in 2020 in one local account — but that reporting used total-registration figures rather than party breakdowns [7].
3. How analysts and private vendors construct “party registration” numbers
Because Illinois lacks party registration, organizations such as L2 Data and derivative projects publish partisan estimates by matching voting history, primary ballots cast, commercial data and modeling; the Independent Voter Project cites L2 as a data collaborator for its Illinois figures [3]. Those third‑party estimates produce charts and claims about partisan registration trends, but they are model outputs and should be treated as inferred, not official, measures [3].
4. What trends can and cannot be demonstrated from available reporting
Available official reporting documents increases or declines in total registered voters and historic turnout levels — notably the exceptional 2020 turnout — but they do not document shifts “by party” at registration because party is not recorded [2] [6] [7]. Any assertion that Democrats, Republicans, or independents gained or lost ground in raw registration rolls in Illinois after 2020 is not supported in the state’s public registration files; such claims come from modeled estimates or national surveys, not the Illinois registration database [1] [3].
5. Alternative sources and their limits: surveys and national compilations
National compilations (e.g., Ballotpedia, multi‑state tables) and surveys provide state‑level views of partisan identification or party‑registration where available — but these sources either combine different methodologies across states or exclude states like Illinois that do not record party on registration forms [8] [9]. Pew, NALEO and other research cite demographic shifts (e.g., Latino population growth) and turnout patterns that can influence partisan strength indirectly, but they do not replace a direct party‑by‑registration time series for Illinois [10] [11].
6. Journalistic bottom line and how to track partisan shifts in Illinois
Bottom line: there is no official time series of “voter registration by party” in Illinois because the state does not record party preference at registration; therefore reported “trends by party” rely on third‑party models or proxy measures (primary ballot choice, turnout by precinct, survey responses) [1] [3]. To monitor partisan shifts reliably in Illinois, follow multiple measures: precinct‑level election returns over time (to infer partisan shifts), primary ballot usage data where available, county registration totals from the State Board of Elections, and independent modelers’ reports — and always note that any partisan registration figure for Illinois is an estimate, not an official registry field [2] [3].
Limitations: available sources do not provide an official party‑by‑registration time series for Illinois; claims about gains or losses by party depend on inference or proprietary datasets [1] [3].