As the 2026 primary season concluded in August, a series of notable polling inaccuracies—from Wisconsin to Michigan and Minnesota—prompted renewed scrutiny of polling reliability heading into the November midterm elections. In some high-profile primaries, polls missed by margins ranging from 10 to 25 percentage points, reigniting distrust among voters still wary after significant errors in the 2016 and 2020 presidential elections.
Despite these primary polling shortcomings, pollsters maintain that such misses hold no bearing on the credibility of general election surveys. Tom Jensen, director of Public Policy Polling, emphasized that primary polling errors have “literally zero” implications for the general election, underscoring the distinct dynamics that separate these contests.
Polling experts attribute difficulties in primary polling to a variety of factors. Primary elections typically draw smaller and less predictable voter turnouts—around 20 percent in 2022 primaries compared to more than 45 percent during general elections—making it challenging to accurately model likely voters. Additionally, turnout fluctuations among demographic groups can skew results, as seen in the 2025 New York City mayoral primary where former Governor Andrew Cuomo’s early polling lead failed to account for an unexpectedly high turnout among younger voters who backed Zohran Mamdani.
Beyond turnout modeling, pollsters face challenges such as nonresponse bias, wherein voters who choose to participate in surveys may not proportionally represent all segments of the electorate. Even if demographic groups are correctly identified, differences within those groups regarding candidate preference can distort poll findings.
Poll volatility in primaries further complicates forecasting. Candidate fields often change rapidly in the weeks leading up to Election Day, with contenders withdrawing or re-entering races, impacting voter dynamics unpredictably. For example, in Wisconsin’s Democratic gubernatorial primary, multiple candidates, including Mandela Barnes and Lt. Gov. Sara Rodriguez, exited late in the cycle, while David Crowley suspended and resumed his campaign multiple times. Polls conducted amid this turbulence showed Francesca Hong as the frontrunner, but Crowley ultimately won, exposing discrepancies exceeding 25 percentage points in late-stage polling.
Undecided voters also contribute to volatility: an average of 18 percent remained undecided in the month before some primary contests this year, leaving substantial potential for shifts in support.
In contrast, general election polls tend to be more stable and accurate, with fewer undecided voters—averaging about 5 percent in recent Senate races in Michigan and Wisconsin—and more established partisan loyalties. General elections also benefit from a greater share of independent, nonpartisan polling firms rather than internal polls sponsored by campaigns or affiliated groups, which made up nearly 45 percent of primary polls in 2026 compared to less than 30 percent in general election surveys.
Industry leaders acknowledge the need to improve polling methods amid ongoing public skepticism. Spencer Kimball, director of polling at Emerson College, highlighted the importance of post-election reviews to diagnose and address errors, citing recent high-profile misfires in New Jersey and Michigan primaries. Pollsters emphasize their commitment to accuracy over electoral outcomes, aiming to restore confidence with rigorous analysis and methodological adjustments as they turn their focus to November’s midterm elections.