Abstract An account is given of the volatility of voters during ten parliamentary election campaigns in Sweden (1956–1988) and ten presidential elections in the United States (1952–1988). For each of these campaigns, the population is described in terms of stable voters, switchers, recruits, armchair partisans, and the unmobilized. Various measures of volatility are explored. There appears to have been a trend over the past 30 years towards increased volatility among Swedish voters, but a similar trend is not evident among American voters. Analyses of the more subjective time of decision measures confirmed this as well. Behind the increased volatility of Swedish voters there has been a loosening grip of the political parties in Sweden. The number and positioning of candidates or viable parties competing for votes are associated with variations in volatility in both countries.