The number of citizens that are undecided in their vote choice has risen in Western democracies. Polling in Britain shows that a significant proportion of the population do not know who they will vote for. Against a backdrop of partisan dealignment and party system fragmentation, there are more parties on the ballot and more citizens ‘free to choose’. Partisanship continues to be important for voting and lacking an identity is a predictor of aggregate voter volatility. A growing literature conceptualises this availability of voters as individual-level electoral competitiveness, stating that undecided citizens are subject to high levels of competition for their vote. I use this framework and apply theory from the decisionmaking literature to offer why these conditions may depress turnout. I construct a measure of undecided voters who are ‘in competition’ and show that this accounts for 40% of the British Election Study Internet Panel respondents. I demonstrate that those who are in competition are less likely to vote. They are more often those without a partisan identity and those who pay less attention to politics, but being in competition is not related to constituency marginality. The results help explain a key determinant of abstention in British elections and suggest low levels of participation may be due to complex choice environments and citizen indecision. However, they provide a positive outlook for pluralistic democracy as voters do deliberate between the party perspectives on offer.