The New York Times report that social conservatives are talking of bolting to a third-party candidate, should Rudy Giuliani get the GOP nomination, is another sign of the disintegrating Reagan coalition.

In truth, that coalition—the 49 states and 60 percent of the nation Reagan won in 1984—was but a Xerox copy of Nixon’s New Majority of 1972. A decade before Reagan won the presidency, Kevin Phillips had already published The Emerging Republican Majority.

To understand why the Republican coalition is disintegrating, one must understand what held it together.

To create a GOP majority in the 1960s, as Nixon did, one had first to identify the voting blocs of the FDR-New Deal coalition the GOP could capture. You go hunting where the ducks are, said Barry Goldwater, though Barry proved not all that good a hunter.

Rockefeller Republicans felt the way to go was to appeal to the trendy media, create little Great Societies at the state level, become more boldly progressive than Democrats on social issues.

Nixon saw that the Democrats who were easiest to win were the non-glamorous working-class types who belonged to unions and backed tough-cop Frank Rizzo in Philly, Mayor Richard J. Daley in Illinois, and Strom Thurmond and George Wallace in Dixie.

Savaged for crafting a “Southern strategy” rooted in race, Nixon had a national strategy, even as he doubled Goldwater’s vote among African-Americans and trebled it in the South. But it was the white vote, 15 times as large as the black vote, that mattered. Nixon carried 67 percent of it. Reagan would carry 64 percent. No matter the Democratic lock on the minority vote, as long as the GOP carried these percentages of the majority vote, Democrats were frozen out of the White House.

Nixon and Reagan brought their Democrats into camp on social and security issues. First was anti-Communism and opposition to the antiwar movement tearing Democrats apart. Second was law-and-order, which meant standing up to urban rioters and campus radicals. Third was social conservatism, defending traditional values in the moral and cultural revolution of the 1960s.

On civil rights, the Nixon position was desegregation, yes, social engineering, no. Nixon integrated the Southern schools that had been 90 percent segregated when LBJ went home. While opposing busing for racial balance, Nixon grudgingly obeyed the court orders.

He promised to nominate Supreme Court justices who would be “strict constructionists,” polar opposite of liberal judicial activists Earl Warren and “Wild Bill” Douglas.

“I should like to have it said of my first Administration that in it the forces of selfishness and of lust for power met their match. I should like to have it said of my second Administration that in it these forces met their master,” railed FDR in his Second Inaugural.

Nixon rallied the New Majority by selecting different targets—liberal media, urban rioters, and student radicals—and stuffing them into the old FDR kill box for round-the-clock bombing.

What is breaking up the Nixon-Reagan coalition?

First, success. With the end of the Cold War, the cause of the Right, anti-Communism, had triumphed. “We are going to do the worst thing we can do to you,” Soviet propagandist Georgi Arbatov said, “We are going to take away your enemy from you.” They did. Without an “evil empire” to fight, the conservative consensus crumbled.

A second cause was shrinkage of the Republican majority as a share of the population because of mass immigration. European-Americans were 88 percent of the nation in 1965. Today the figure is 66 percent. Hispanics are a rising share of the vote in California and the West, and, as they are poorer and less educated, they vote for the party of government, not the party that will cut taxes on capital gains and estates they do not have.

A third cause of GOP malaise is that the social revolution of the ’60s has converted a vast slice of the nation. Where Nixon carried California five times on national tickets and Reagan all four times he ran, Democrats have won it handily in the four elections since 1992.

Just as Bill Clinton, in losing both Houses in 1994, presided over the last stages of realignment begun by Nixon and Reagan, George W. Bush is presiding over the death of the Nixon-Reagan coalition.

What killed it is Wall Street Journal conservatism: a disastrous and unnecessary war; a preferential option for the rich; open-borders immigration; a free-trade fanaticism that is denuding America of manufacturing jobs, sinking the dollar, and growing our dependence on foreign goods and foreign loans.

Now the GOP frontrunner is a New York mayor who is pro-choice, pro-gun control, pro-affirmative action, marches proudly in Gay Pride parades, and presided over a sanctuary city for illegal aliens. And the Right let it happen.