The study of political realignments, or realigning elections, is concerned with a rare, significant, long-term shift in the voting behavior and party identification of the electorate. In a journal article on critical elections, published in 1955, and an article on secular realignment in 1959, political scientist Valdimer Orlando Key Jr defined a critical election as "a type of election in which there occurs a sharp and durable electoral realignment between parties."
Later Key Jr adopted the term "secular realignment," characterizing a critical election as a "secular shift in party attachment." Key Jr defines it as a shift of the electorate from party to party, extending over several elections and appearing not to be affected by the peculiar factors that influence the vote at individual elections.
Political realignments are usually a result of some profound shock to society, such as a massive economic downturn, like the Great Depression after 1929 in the United States. Such shocks energize voters to come to the polls and lead some to change their political allegiances. After realignments, there is a new period of political stability.
Before a realignment, the behavior of the electorate is predicable. After it ends, voters act the same way again in their new configuration. In the United States, after 1932, the Democratic party under Franklin D. Roosevelt dominated the national government for a generation, enacting a variety of unprecedented legislation to deal with the economic situation and then world war. In the United Kingdom, the 1945 post-war election was also one of realignment, installing the Labour party which introduced radical legislation on nationalization of key industries, education, social security and pensions, and the National Health Service.
Thus, realignments have marked precise dividing points between different eras and supplying a critical dynamic for the peaceful change within political systems. However, since the 1960s, there have been shifts in the external environment of politics related to broad economic and social transformations of society, such as the growth of a more educated population that is less readily mobilized and the rising power of the media in shaping political attitudes. These changes have resulted in increasingly volatile popular voting and a lack of new realignments.
For much of American history, the major political parties have enjoyed a remarkable partisan stability among voters. Voters expressed a rock-like support at the polls in election after election, allowing one of the parties to win most contests in an era and dominate government policy. There have been five times when these long periods of stability were interrupted, beginning in elections in 1800, 1828, 1854, 1894, and 1932. Every time, with old issues losing their force and new pressures emerging, a particular calamity sparked forces strong enough so that the elements comprising the political world could be overturned and then realigned.
However, since the 1960s, election outcomes in the United States, the United Kingdom and in much of western Europe have been a result of fluctuating short-term forces, including the attractiveness of a certain candidate, or the influence of a dramatic episode, including an incident of racial violence during an election. These driving forces mark a significant shift from the stable, deeply imbedded partisan loyalties. The voter realignment from parties has resulted in a significant change in the political process.
In the main, especially in states where two political parties dominate, such as the U.S. and the U.K., the majority of voters will continue to vote for one party throughout their adult lives, with the outcome of elections swayed by a relatively small body of "floating voters," who may change their allegiance between elections, or the outcomes of key marginal constituencies seeing control shift to one party or the other. When political realignment occurs, large numbers of established voters change their allegiance, as in the British General Election of 1979 when Margaret Thatcher, by appealing to traditional, working class Labour voters, won a landslide election which would see her Conservative party rule for 18 years.
Such an effect is less observable in countries where more than two parties have some power and influence. From the 1990s in the United Kingdom, there has been growth in nationalist parties in Wales and especially Scotland which have greatly complicated politics, making electoral behavior less predictable. In western Europe, new social movements have developed, and the emergence of environmentalists, Green parties, have also complicated voting behavior.