In truth, it was both. Phillips’s projection was grounded in his assessment of recent Republican strategies. At the same time, he asserted that his analysis offered the best hope for the party’s future: pitting racial and ethnic groups against one another and capitalizing politically on the competitions and resentments that followed. “The whole secret of politics,” he told the journalist Garry Wills during the 1968 presidential campaign, is “knowing who hates who.”

That year, the GOP had convincing reasons for following Phillips’s lead. The segregationist Governor George Wallace made a strong showing in the South and elsewhere with a shoestring campaign as an independent, demonstrating that opposition to integration played well with some working- and middle-class white voters. Phillips saw the potential: If Republicans exploited tensions over civil rights, he argued, they could attract white voters in traditionally Democratic southern states, as well as in the Midwest and West. And if Republicans won those voters, they’d win the mantle of power too.

Fifty years later, it’s tempting to draw a straight line from The Emerging Republican Majority to the Republican Party today. The GOP has come to dominate every part of the Sun Belt, just as Phillips predicted, and President Donald Trump has mobilized the politics of division in a way no modern president has before. “Objects in the mirror really are closer than they appear,” Louis Menand wrote in The New Yorker last year. “It’s not that far from Wallace to Trump.”

But a closer look at the initial reception to The Emerging Republican Majority shows that the line to Trump is less clear. Despite Phillips’s position in the Nixon White House, administration officials were deeply divided over the book’s recommendations. Nixon had won the Republican nomination by forging a centrist path between the liberal Nelson Rockefeller and the conservative Ronald Reagan, and then won the presidency by similarly positioning himself between the liberal Democrat Hubert Humphrey and the conservative populist George Wallace.

Moving to the right on racial and social issues seemed risky to many in the Nixon camp, but some enthusiastically supported the idea. The administration waffled between right and left for two years, but in the 1970 midterms went all in with a strategy to exploit racial and social divisions in campaigns across the Sun Belt. Phillips’s critics turned out to be right: The results were dismal. When Nixon acknowledged as much after the election, he promised to pull himself back to the center.

But the strategy didn’t die with Nixon. It would be revived, combined with a new emphasis on social issues, and used to great success in the 1980s to secure the Republican majorities that Phillips had prophesied. Now President Trump is exploiting racial and social divisions even more aggressively than did Nixon in the 1970 election—and in the process, he risks consigning Republican majorities to the past.