Voting behaviour in referenda and elections: Undecided voters and the assessment of risk

In both elections and referenda some voters will know how they are going to vote far in advance while other ‘undecided voters’ will make up their mind closer to when they cast their ballots. Undecided voters are key players in both elections and referenda, as campaigns may have little influence on those who have already made up their mind although they can sway these undecided voters one way or another. What factors influence the vote choices of undecided voters and how does it vary between referenda and elections? We hypothesise that undecided voters will be more likely to vote no in referenda, and vote for minor parties in elections, based on different risk assessments in these different types of voting events. To test this hypothesis we draw upon the Australian case using data from the Australian Election Study and the Australian Constitutional Referendum Surveys spanning 25 years from 1998 to 2023. We use data on voting behaviour in three referenda on: Australia becoming a Republic (1999); same sex marriage (2017); and the Indigenous Voice to Parliament (2023). We compare referenda voting with voting in Australian federal elections from 1998 to 2022. This paper sheds insights into the differences between voting in referenda and elections, voter assessments of risk in their political choices, and the behaviour of undecided voters.