How opinion polls affect voting in Bangkok's gubernatorial election

Abstract

In response to the widely publicized failure of most pollsters to predict the winner of the Bangkok governor election on 3 March 2013, this study examined the published results of opinion polls in the news media to see how they had affected the voter preference and what errors existed. The study analyzed a series of poll results by five major pollsters for the pre-election and exit polls during the governor election campaign from January to March 2013 and, then, compared them with the final results of governor election. The poll results lent partial support to the spiral of silence theory. Among all pollsters, only NIDA Poll projected the right prediction for Democrat candidate M. R. Sukhumbhand Paribatra as the winner. Its pre-election polls showed his final victory occurring in the last leg of the election campaign as a result of the late swing voters against the ruling Pheu Thai Party attaining monopoly on power. Suan Dusit and Abac Polls showed the existence of the bandwagon effect for Pheu Thai candidate Pol. Gen. Pongsapat Pongcharoen. Besides their polling effects, major factors accounting for errors included shy Democrat factor, late swing of voters, sampling error, and nonresponse bias.