Quebec 2018: A Failure of the Polls?

The polls of the 2018 Quebec election forecast a close race between the two leading parties. The result, a clear victory of the Coalition Avenir Québec (CAQ) over the Parti libéral du Québec (PLQ), was clearly at odds with the polls. We argue that when the polls get it wrong, it is important to determine whether there was a polling miss, in which the discrepancy is due to changing voter behaviour, or a poll failure, in which the problem stems from polling methodology. Our post-election poll shows that changing voter behaviour—last-minute shifts and the vote of non-disclosers—explains most of the discrepancy. These movements varied by region. We conclude that the Quebec 2018 election was among the worst polling misses in history but not necessarily a major poll failure.