Why polling primary elections is so hard

Key Points:

• Francesca Hong, a Democratic Socialist candidate for Wisconsin governor, narrowly lost her 2026 primary by less than 0.5%, despite being heavily outspent and initially leading polls by 20 points, highlighting a significant polling discrepancy.
• Historical data shows primary election polls have an average error margin of about 13 points and often fail to predict winners accurately, with some races missing by over 30 points, making primary polls less reliable than general election polls.
• Primary polls are particularly challenging due to factors like unpredictable voter turnout, late changes in candidate support, and fewer reliable demographic predictors, leading to greater uncertainty and error in polling results.
• Analysts caution against interpreting polling errors as ideological bias, noting that both progressive and centrist candidates have experienced significant polling misses, and emphasize the need to treat primary polls with appropriate skepticism.
• The key takeaway is to view primary polls as rough indicators rather than precise forecasts, expecting occasional large errors and avoiding overconfidence in early leads to better manage expectations throughout election cycles.