How voting intentions evolved: A view from Quebec
by Claire Durand with Mélanie Deslauriers
Citizens and pundits not infrequently complain that there are too many polls during election campaigns. But the large volume of polls has many advantages. First, people do not have to rely on a single source of information on the state of public opinion. When polls give different readings of the situation, we are able to put the numbers into perspective and are reminded that the margin of error in polls is real. Second, researchers and voters can trace the evolution of public opinion throughout the campaign, and get an objective measure to set against politicians’ claims as to the level of support for their parties or policies.
The polls showed substantial shifts in voting intentions in the course of the recent federal election campaign, especially in Quebec. In the end, the polls predicted the results quite accurately for some parties, but not for others. In what follows, I look at the apparent evolution of voting intentions, analyze the discrepancy between the polls and the actual vote, and comment on the polling methods used.
In Quebec, where it all started …
To trace the apparent evolution of voting intentions, we assembled the published estimates of 58 polls1 conducted in the 53 days between August 20, two and a half weeks before the election was called, and October 11, three days before the election. The results of these polls were then spread over the days when they were in the field, and we took the average of all the polls that were in the field on a given day. We used this information to trace the apparent evolution of the polls using time-series analysis.
Figure 1 displays what these analyses tell us about the evolution of support for the different parties in Quebec.2 At the beginning, the Bloc had a narrow lead with a little over 30 per cent, while the Conservatives and the Liberals were virtually tied at about 25 per cent and the NDP was trailing at about 12 per cent. By early September, voting intentions for the Liberals began to drop to the benefit of the Conservatives. In mid-September, after one week of campaign, the Conservatives were in a tie with the Bloc at around 30–32 per cent. At that time, it seemed to observers that anything was possible and that the Conservatives could “take” the province.