What creates such change? Obviously, part of it is electoral reality. In 1948, Henry Wallace tested the proposition that a candidate who had accepted the Communist Party’s endorsement could attract widespread support. He won 2.4 percent of the vote. In 1972, George McGovern tested the proposition that America would embrace a candidate who called for ending not merely the Vietnam War, but the Cold War itself. He won a single state.

That’s part of what’s happening in the Republican Party now. GOP elites are pushing back against Donald Trump because the 2008 and 2012 elections taught them that demonizing Mexican immigrants is political death.

But such shifts aren’t only political. The Republican South Carolina legislators voting to take down the Confederate flag aren’t doing so because they fear losing their seats. NASCAR and the PGA aren’t cutting ties with Trump because they’re worried about the GOP’s fortunes in 2016.

Politicians alone can’t render a once-acceptable opinion beyond the pale. They need allies in the cultural and economic sphere. It wasn’t only Harry Truman who defeated Henry Wallace and the pro-Soviet left. In the late 1940s, some of America’s most important intellectuals—men like Arthur Schlesinger Jr. and Reinhold Niebuhr—began arguing that communism was as anathema to liberalism as was fascism. In the early 1970s, it wasn’t only Democratic bosses like Chicago mayor Richard J. Daley who loathed McGovern. An entire community of intellectuals—the early “neoconservatives”—revolted against McGovernism. Some of these intellectuals, like Irving Kristol and Norman Podhoretz, migrated to the political right. But others, like Daniel Bell, Daniel Patrick Moynihan, and Nathan Glazer, remained on the left. In the 1980s, they were joined by The New Republic and the Democratic Leadership Council, institutions that waged a successful intellectual campaign to make McGovernism unacceptable on the mainstream left.

If cultural elites helped render certain left-wing views unacceptable in the 1940s, 1970s, and 1980s, economic elites are helping render certain right-wing views unacceptable today. David Brooks foresaw this phenomenon fifteen years ago when he wrote Bobos in Paradise, arguing that corporate America was embracing the liberal-cultural ethos of the 1960s. In 2003, Intel, Merck, and Boeing all filed briefs urging the Supreme Court to uphold affirmative action in college admissions. Earlier this year, Goldman Sachs, Google, and Coca-Cola urged the Court to legalize same-sex marriage. In South Carolina, the state’s chamber of commerce and manufacturer’s association lobbied Governor Nikki Haley to remove the Confederate flag. And since Trump’s comments about undocumented Mexican immigrants, he’s faced harsher retribution from many of the corporations he does business with than from the Republicans he’s running against. If Democratic Party leaders once needed liberal intellectuals to marginalize Wallace and McGovern’s views about communism, Republican leaders need corporate America to marginalize the anti-gay rights, anti-Mexican, pro-Confederate flag wing of their party today.