Although the existence of strategic voting in the United Kingdom and Canada has been well documented, quantifying when a voter will cast a strategic ballot has yet to be done. This article draws on electoral data from five UK and Canadian elections in order to address this gap by identifying a precise “tipping point” for when a non-viable party supporter's probability of voting strategically crosses a 50 per cent threshold. I find the best tipping point measure occurs when a voter rates their favourite viable party greater than 59 out of 100 in the UK and greater than 73 out of 100 in Canada. Both countries also have clear tipping points for the likeability of an individual's highest preferred party and perceptions of that party's distance from contention. Overall, by calculating these tipping points, researchers can better gauge voter behaviour and how, or when, certain factors contribute to strategic voting.

Voters are deterred from casting a vote and more likely to vote strategically if their preferred choice is less competitive in their electoral district. We use 2019 Canadian Election Study data to show that respondents’ answers to a “how likely are you to vote” question depend on their estimate of their preferred party's local chances of winning, relative to other parties. This deterrent effect on turnout from the competitiveness of a voter's preferred party is concentrated among certain parties (NDP, Green, People's Party of Canada). Under first-past-the-post (FPTP), voters with particular policy perspectives are systematically deterred from voting, relative to other voters. Furthermore, we find that despite supporters of all parties having an incentive to vote strategically if their party is outside the top two in the district, strategic voting is heavily concentrated among voters who prefer parties other than the nationally most competitive two parties.