Glossary
Plain-English definitions
30 polling and political terms used on this site.
- Approval rating
- The percentage of respondents who say they approve of an officeholder's job performance. Reported alongside disapproval; net approval = approve − disapprove.
- Ballot measure
- A proposition appearing on a ballot for direct voter decision (initiative, referendum, constitutional amendment, bond, or legislatively-referred question).
- Bellwether
- A county, state, or demographic that historically votes with the eventual winner. Reliability fades in polarized cycles.
- Class of senator
- Each US senator belongs to one of three rotating classes (1, 2, 3). Only one class is up for election in any given cycle. 2026 is Class II.
- Crosstabs
- Subgroup breakdowns of a poll (by age, race, education, region). Often noisy because subsample sizes are small.
- Electoral College
- 535 electors (538 incl. DC) who formally elect the president. Each state's allocation = senators (2) + house seats.
- Favorability
- Whether respondents view a person favorably or unfavorably, separate from voting intent.
- Generic ballot
- A poll question asking which party respondents will support for Congress, without naming candidates. Best read as a directional national signal.
- House effect
- A pollster's persistent tendency to overstate one side. Computed by comparing each pollster's polls to the broader consensus.
- Incumbency advantage
- The historical electoral edge sitting officeholders enjoy from name recognition, fundraising, and constituent service. Has narrowed in recent cycles.
- Kalman filter
- A state-space model that estimates a latent “true” value from noisy observations. Used here as one of the six aggregation methods.
- Likely voter (LV) screen
- A pollster's method for filtering registered voters down to those most likely to actually vote. Methods vary widely.
- LOESS
- Locally weighted scatterplot smoothing — a non-parametric regression that produces a smooth trend line less sensitive to outliers.
- Margin of error
- The 95% confidence interval around a poll's reported number, scaling with √(1/n). For a typical 600-person poll: ±4 pt.
- Monte Carlo
- A simulation method that draws thousands of random samples from each race's probability distribution to estimate chamber-level outcomes.
- Oversample
- Deliberately surveying more respondents from a small subgroup to improve subgroup precision; weighted back to its true share for the topline.
- Partisan pollster
- A pollster affiliated with a campaign, party, or political organization. Their polls are stored but flagged separately and weighted carefully.
- Primary vs general
- Primary election polls measure intra-party preference; general election polls measure D-vs-R matchups. Methodologies differ.
- PVI
- Cook Partisan Voting Index — how much a district leans left or right of the national average across the last two presidential cycles.
- Rating shift
- When a race rating changes — e.g. Tossup → Tilt D. Tracked for both poliagg and external raters.
- Registered voter (RV) screen
- A poll of registered voters, before applying any likely-voter screen. Tends to slightly favor Democrats vs LV samples.
- Right track / wrong track
- A standard question asking whether the country is on the right or wrong track. Predictive of incumbent-party performance.
- Safe seat
- A race where the rating is Safe D or Safe R — incumbent or party advantage exceeds 15 points.
- Split-ticket
- When a voter chooses candidates from different parties for different offices (e.g. R for President, D for Senate). Has declined since 2010.
- Topline
- The headline number from a poll — the candidate-vs-candidate result before crosstabs. What gets quoted in the news.
- Tossup race
- A rating used when polls and fundamentals indicate a margin under 0.5 points. Closest possible bucket on the 9-tier scale.
- Tracking poll
- A poll repeated frequently (often daily) by the same pollster, with rolling samples to detect short-term shifts.
- Turnout
- The share of eligible voters who actually cast ballots. The biggest cycle-to-cycle source of margin variation.
- Two-way margin
- The difference between the top two candidates' shares (D% − R%), ignoring third parties and undecideds.
- Weighted average
- A polling average where each poll is weighted by sample size, recency, and pollster accuracy — vs an unweighted mean.