Donald Trump, the abrasive and ugly face of the Republican Party who will likely be the party's nominee for president, is the latest and worst manifestation of a drift that has been going on among American conservatives for more than half a century.
The starting point for that drift toward a narrow right-wing ideology is impossible to pinpoint. It developed in the West, especially California in the 1950s, and crystallized for the first time in Arizona Senator Barry Goldwater becoming the party's nominee in 1964.
The Goldwater revolution ("In your heart, you know he's right") rolled over the party's moderates, including their preferred candidate, New York's Nelson Rockefeller, at a 1964 party convention made memorable by Mr. Goldwater's declaration that "extremism in the pursuit of liberty is no vice; moderation in the pursuit of justice is no virtue."
The word "extremism," then as now, was loaded, because it indirectly referred to the racist John Birch Society that was making its influence felt within GOP ranks. Party moderates viewed the Birchers with loathing, but Mr. Goldwater's remarks served to legitimize them. The door then cracked open for other extremist groups and ideologues to influence the Republican mainstream.
Mr. Goldwater led the Republicans to a crushing defeat in 1964, which allowed a triumphant Democratic President Lyndon Johnson to introduce his Great Society spending programs and to promote civil rights in the South. Mr. Johnson, a Texan, remarked when he signed civil-rights legislation that he was signing away the South for the Democratic Party. True enough. The South turned sharply to the Republicans as part of President Richard Nixon's "Southern strategy."
Northern moderates, by the standards of the time, had dominated the GOP. The party of such leaders as Thomas Dewey, Dwight Eisenhower, Henry Cabot Lodge, Leverett Saltonstall, Charles Percy, Everett Dirkson and Mr. Rockefeller had changed by the 1970s in the face of "sagebrush" westerners such as the followers of Mr. Goldwater and Southern quasi-segregationists.
Mr. Nixon held the coalition together with considerable shrewdness. His phrase, "the silent majority," spoke to a backlash against civil rights and other movements that had roiled the country in the 1960s. It is to today's "silent majority" that Mr. Trump appeals – people who feel threatened, ignored and belittled by "elites" of all kinds.
Once Republican strength grew in the South, so did the influence of Christian evangelicals because evangelicals were, and are, disproportionately found there. (Tennessee, for example, has the highest share of adults self-describing as "evangelicals.")
Ronald Reagan's search for the nomination, and then his election as president in 1980, turned traditional Republican skepticism about the size of government into a full-scale rhetorical assault. The assault had undertones: that government spending was going disproportionately to blacks and interest groups.
The assault was particularly attractive to white working-class men who felt threatened by affirmative action for blacks and welfare programs for those without work. The government, which in President Franklin Roosevelt's time had been considered the workers' friend, was now the workers' foe, taking hard-earned money from paycheques and redistributing it to undeserving others.
Meanwhile, the Supreme Court loosened rules on political contributions and spending, so that money began to flow in unheard-of quantities into all parties. Very rich and very right-wing donors bankrolled campaigns by those who shared their views, including challengers of Republican incumbents deemed not ideological enough. Incumbents had to tilt ever further to the right to protect themselves from losing nominations, as some did in recent years to Tea Party activists.
State legislatures, in charge of redistribution, gerrymandered congressional districts to provide more and more "safe" seats, where the competition became not between Democrats and Republicans but between Republicans for the nomination, with each aspirant appealing only to the party's ideological base. The more incendiary the rhetoric, and the more fierce the promises to remake the government in Washington, the deeper the disillusionment among the GOP base that for all the talk, very little changed in Washington.
They blamed Democrats, and especially that black, liberal president. But they also fingered Republicans who had sold out in Washington, forgotten their promises, cosied up to moneyed interests and were therefore complicit in a "system" that had frozen out their concerns.
Years of battering government, pandering to right-wing media, letting extremist talk filter into the party and playing footsie with coded language created the conditions for Republicans to be Trumped by all these vices.