Before the organized movement, moderate perspectives on the issues were adopted by a variety of public officials who weren't inclined to govern in a strictly liberal or conservative pattern.
U.S. presidential politics in the 1950s and early 1960s was dominated by just this sort of moderation. President Eisenhower was a moderate pragmatist who initially had difficulty deciding which party best represented his views. He was followed by President Kennedy, who implemented generally conservative economic policies while simultaneously adopting progressive views on civil rights and foreign policy.
The term "centrist" wasn't used at the time to describe this political style. But it subsequently inspired and influenced early centrist organizers.
The political environment for movement centrism in the U.S. was largely established in the 1960s and 1970s. It can be traced to the new round of government expansion that began with Lyndon Johnson's "Great Society," and to the legalization of abortion in 1973 with Roe v. Wade.
Some Democrats came to disagree with the growth of government and reliance on large-scale social programs. Meanwhile, the Republican party became increasingly identified with the opponents of legal abortion and their culturally conservative politics, which some viewed as divisive.
Thus, you had an emerging Democratic faction that disagreed with liberal economic and fiscal policy, and an emerging Republican faction that disagreed with conservatives on cultural issues such as abortion and gay rights.
Centrist Democrats established the Democratic Leadership Council, and achieved the most dramatic early electoral success when former DLC chairman Bill Clinton became president in 1992.
Moderate Republicans were already in office in significant numbers. They began to gather in groups like the Republican Main Street Partnership and to advocate an emerging centrist politics of fiscal responsibility combined with social tolerance.
In Clinton's early term as president, centrist politics largely failed to materialize. But he turned back to the center following a stinging defeat in midterm elections that brought Republicans into the majority of both houses of Congress.
It was the popularity of Clinton's centrist style and easy reelection in 1996 that became an inspiration and catalyst for center-left parties in Europe, presaging the rise in 1997 of Tony Blair and the New Labor party in Britain, and in 1998 of Gerhard Shroeder in Germany.
Centrist Democrats in the U.S. and center-left parties in Europe have shared ideas and adopted a new basic philosophy that emphasizes competitive enterprise, fiscal discipline, and individual empowerment rather than a reliance on redistributive entitlement programs. Thus, there is a new acceptance of what would traditionally be viewed as conservative economic and fiscal ideas, but a continuation of traditional liberal views regarding social tolerance and diversity.
Meanwhile, centrist Republicans in the U.S. have embraced traditionally liberal cultural policies, while maintaining their traditional emphasis on economic and fiscal conservatism.
In essence, centrism has emerged as a philosophy combining traditionally conservative concerns regarding the economy and fiscal discipline, with traditionally liberal concerns regarding social tolerance.
While the centrist movement has followed a distinct path of emergence in the U.S. and Europe, it should be noted that center parties emerged much earlier in various parts of the world. There are center parties in Sweden, Finland, Norway, Israel, and Estonia, and most parliamentary democracies have a party that positions itself between left and right.
These parties are philosophically and programmatically diverse, as might be expected in widely differing circumstances in different parts of the world. There is often a tendency, however, to adopt some of the economic views of the parties to their right and the cultural or social views of parties to their left.