Failure and Success in Political Polling and Election Forecasting

Did “Trumpists” Perform Worse in US Senate Election Polls?

“…Our results therefore point to a systematic bias in US pre-election polls that affects not only Trumpists but all Republican candidates who have run in recent contests. 1,3,5,9 Thus, whatever Trump has in common with the candidates he has endorsed, these characteristics do not appear to explain why support for Republican candidates has been underestimated by pre-election polls.…”

“…A major challenge in forecasting elections from polls is that polling organisations need to predict which of their respondents are likely to vote 3 . So, a second popular narrative speculated that these “likely voter” models were incorrect.…”

“…A major challenge in forecasting elections from polls is that polling organisations need to predict which of their respondents are likely to vote. 3 So, a second popular narrative speculated that these "likely voter" models were incorrect. With his unusual characteristics and antics, Trump might have drawn new voters to the ballot box, so the composition of his supporters diverged substantially from what the likely voter models predicted.…”

“…For example, the people taking part in the polls might not be representative of the population of interest as certain types of voters might refuse to take part in polls. Or, when voters do take part, they might tell pollsters they plan to vote one way and then do the opposite – either because of deliberate misreporting or because they genuinely change their minds in the closing stages of a campaign 3 . These and other sources of error can lead to biased polls if they cause an over‐ or underrepresentation of voters with distinct political preferences.…”

Pesquisas eleitorais no Brasil: tendências e desempenho

“…Não obstante a existência de fatores relacionados aos erros em surveys eleitorais, a evidência sistemática de diferentes países mostra que pesquisas nas semanas que antecedem um pleito fornecem, em média, estimativas razoavelmente precisas do que a apuração dos votos revelará -erros têm, ao contrário, apenas diminuído ao longo dos anos (Jennings;Wlezien, 2018). Em certo sentido, dadas as dificuldades envolvidas de se desenhar planos amostrais com informações nem sempre atualizadas e em meio a diferentes fontes não aleatórias de erro, é surpreendente o desempenho das pesquisas eleitorais ao antecipar tendências e resultados, ainda que esse não seja o objetivo ou a função das pesquisas (Gelman, 2021).…”