Late-Deciders and Open Primaries Upend Wisconsin and Michigan Polls

Two recent Democratic primary results underscored polling limits: in Wisconsin, Crowley pulled off an upset as final polls underestimated his support and overestimated undecideds, aided by Hong’s missteps and late shifts as voters coalesced around Crowley; in Michigan, El‑Sayed narrowly defeated Stevens despite polls showing him ahead, a gap attributed to nonresponse bias and a tendency for younger voters to skew results in an open primary. Pollsters caution that primary polling is harder due to turnout volatility, race dynamics, and late entrant/exits, suggesting focus on candidate shares rather than margins and recognizing that late deciders can flip outcomes.