Since 1960 turnout has declined in presidential elections, and since 1966 it has declined in off-year congressional elections. These declines occurred despite several major trends that could have increased electoral participation. An analysis of the eight SRC-CPS presidential election surveys conducted between 1952 and 1980 and of the six SRC-CPS congressional election surveys conducted between 1958 and 1978 suggests that these declines may result largely from the combined impact of two attitudinal trends: the weakening of party identification and declining beliefs about government responsiveness, that is, lowered feelings of “external” political efficacy. Between two-thirds and seven-tenths of the decline in presidential turnout between 1960 and 1980 appears to result from the combined impact of these trends. Data limitations hinder our efforts to study the decline of congressional turnout, but approximately two-fifths to one-half of the decline between 1966 and 1978 appears to result from the combined impact of these attitudinal trends.