The historic victory of Barack Obama contained many dramas, but none was more important than the climactic turn it symbolized in the present-day fortunes of two outsize forces in recent political history — the civil rights movement and the conservative movement.

Together they have probably been the most powerful engines of political change during the past half-century, but they have also exacted large demands from the two parties and their leaders. And it happened again in this election.

For Senator Obama, the fraught alliance between the civil rights movement and the Democratic Party was a persistent though unwelcome theme in this campaign — whether it was the crisis occasioned by the recorded sermons of the Rev. Jeremiah Wright or the defeats Mr. Obama was dealt in the primary by blue-collar voters whose distrust of him seemed to replay the racial anxieties of the 1960s, when civil rights protest loosed a white “backlash” that divided the Democratic Party.

John McCain, for his part, was haunted by his uneasy and at times hostile dealings through the years with the movement conservatives who helped elect every recent Republican president. In choosing to solicit their support, Mr. McCain alienated the moderates and independents who ultimately deserted him.

The tangled nexus between movements and parties has been complicating American politics since the middle of the 19th century. To a great extent, both major parties owe their identities to movements.

The modern Democratic Party was shaped by the populism of the 1890s, the antibusiness reformism of the 1930s and the civil rights crusade of the 1960s. The Republican Party was formed by abolitionism in the 1850s, anti-Communism in the 1950s, antitax revolts in the 1970s and 1980s and the evangelical conservatism of the 1990s and 2000s.

In each instance, a movement and a party came together. But the partnership was seldom satisfactory to either side. This isn’t surprising. While movements are driven by specific causes (punishing “robber barons,” ending “big government”), parties stay relevant by adjusting to new conditions....