How has Illinois voter registration by party changed since 2020?

1. What the official numbers say: larger rolls, slightly lower turnout than 2020

The Illinois State Board of Elections’ certified 2024 totals list 8,101,424 registered voters and show 5,705,246 ballots cast — a 70.42% turnout in 2024, down from the 73% turnout Illinois recorded in 2020 according to state reporting cited by local outlets ^{[1] [2]}. The board maintains public registration-count files that are updated daily and that reflect jurisdiction-reported active registrations; researchers and journalists use those files to measure roll size and partisan composition over time ^{[3] [4]}.

2. Party registration tracking: sources and limits

Detailed party-by-party registration breakdowns for Illinois are compiled both by the State Board of Elections (raw counts) and by third-party projects such as the Independent Voter Project, which partners with data vendors to estimate partisan shares and trends ^{[3] [5]}. Official SBOE files provide the authoritative totals but do not interpret long-term partisan dynamics; independent aggregators apply methods (and assumptions) to produce partisan trends, and their methodologies should be reviewed when comparing numbers ^{[3] [5]}.

3. Trends since 2020: growth in registered voters, mixed signals on party shifts

Available sources establish that Illinois’s registered-voter pool remained high through 2024 and into 2025 (8.1 million registered in 2024) but do not provide a simple narrative about steady partisan realignment in electorate composition; partisan-change claims rely on disaggregating SBOE counts or using third-party estimates ^{[1] [3] [5]}. The Independent Voter Project publishes partisan registration snapshots and percentages (updated as of Aug. 27, 2025 in their dataset), but those figures are derived from L2 Data estimates and are separate from SBOE raw counts ^[5]. In short: total registrations rose and turnout fell from the 2020 peak, but party-by-party shifts require consulting SBOE time-series files or independent reconstructions ^{[3] [5]}.

4. Why 2020 stands out and how that affects comparisons

Illinois’s 2020 turnout was an outlier — the state hit a 73% participation rate amid the pandemic-driven surge in vote-by-mail and early voting — and 2024 returned to a somewhat lower level (70.42%) even as early and mail voting remained high ^{[2] [1]}. Comparing party registration before and after 2020 without accounting for the unique turnout and administrative changes in 2020 risks overstating permanent partisan realignment; the Census Current Population Survey and other national datasets note that 2020 produced unusually high engagement nationally as well ^[6].

5. What the public datasets let you measure — and what they don’t

Researchers can measure raw registration totals, active-voter counts by party, and turnout for each election using SBOE exports and election result pages; the SBOE cautions these counts are unofficial snapshots that change as jurisdictions update their statewide database ^{[3] [4]}. What these datasets do not automatically provide are causal explanations for party shifts (migration, naturalization, registration drives, or partisan switching), and independent data vendors’ partisan attribution methods vary ^{[3] [5]}.

6. How to get a reliable party-change picture

To map how party registration changed since 2020, analysts should download SBOE registration-count files at multiple time points (quarterly or annual), cross-check with the SBOE election result databases, and (if using third-party partisan estimates like L2/IVP) read the vendor methodology to understand how they infer party affiliation from registration behavior ^{[3] [5] [4]}. Public researchers may also compare to Census and CPS voting supplements for turnout context, but those sources report survey estimates rather than official registration rolls ^{[6] [7]}.

7. Bottom line and caveats

Bottom line: Illinois’s registration rolls remained large after 2020 — the state reported about 8.1 million registered voters in 2024 with turnout at ~70% — but claims about substantive party realignment require careful use of SBOE time-series files or third‑party partisan estimates, each with known methodological limits ^{[1] [3] [5]}. Available sources do not provide a single, definitive narrative of party-by-party change since 2020; they point instead to authoritative counts (SBOE) and to vendor-based partisan breakdowns that must be interpreted in light of their methods ^{[3] [5]}.