Paul Ryan’s decision to retire from Congress is being interpreted as a sign by many that Republicans will do poorly in the midterm elections. That may be true, but Ryan’s exit also symbolizes a broad shift that has taken place within the party. It marks the end of the Reagan revolution.

The GOP of the 1950s and ’60s was the party of American business, drawing broad support from white-collar professionals and country-club businessmen. It had a straightforward Chamber of Commerce orientation, arguing for low taxes, few regulations and fiscal responsibility. But it was a minority party, willing to go along with the basic contours of Franklin Roosevelt’s New Deal.

To understand the extent of Roosevelt’s imprint on American politics in the mid-20th century, consider: From 1933 to 1969, the only men who occupied the Oval Office were FDR, fervent disciples of FDR, or in the case of Dwight Eisenhower, a general handpicked and promoted by FDR. It is said that when entering the White House in 1969, Richard Nixon’s already healthy paranoia grew, because he believed, not without reason, that he was a lonely Republican in a federal government that had been stacked with liberals for almost half a century.

In foreign affairs, the Republican Party in the 1950s had only recently shrugged off its isolationist posture but was still cautious about international engagement. On civil rights, the party was progressive and activist. Chief Justice Earl Warren, a former Republican governor, issued the Supreme Court’s landmark decision outlawing school segregation, and President Eisenhower dispatched federal troops to Arkansas to enforce the ruling.

Nixon ushered in the beginnings of the party’s first transformation. The party had long had a nationalist and nativist side, but Democratic President Lyndon Johnson’s embrace of the civil rights movement created the circumstances for one of the great flips of American history. The Democrats, heretofore the party of the Jim Crow South, became the party of civil rights, while the Republicans, the party of Lincoln, began to mirror the resentments of Southern whites against the federal government and civil rights legislation. But in other areas of domestic policy, Nixon governed as a liberal. He created the Environmental Protection Agency and managed the economy much like any Democrat would have. “We are all Keynesians now,” he is famously quoted as saying.

Reagan finished what Nixon started, turning the GOP into an ideologically oriented party, staunchly advocating free markets, free trade, limited government and an enthusiastic internationalism that promoted democracy abroad. The old country-club Republicans were never true believers, but they accepted Reagan’s redefinition after its electoral success, as demonstrated by the alliance between the Gipper and his vice president, George H.W. Bush.

The Reagan redefinition of the party, as a quasi-libertarian organization, persisted through the Clinton years, though the GOP always continued to bring along its socially conservative base. The party leaders and its official ideology were Reaganite.

Then came Donald Trump. Early on, Trump seemed to recognize that the Republican Party had changed and that the core ideological appeal was no longer about economics but nationalism, race and religion. His first major political cause was birtherism, the noxious and false claim that President Obama was secretly a Muslim born in Kenya.

When Trump ran for the Republican nomination in 2016, he was virtually alone on the podium in rejecting the Reagan formula. He dismissed any prospect of entitlement reform, while criticizing foreign interventions and democracy promotion. Even on free-market economics, he flirted with all kinds of liberal ideas, from big infrastructure spending to universal health care.

But he was consistently hard line on a few core issues — immigration, trade, race and religion. On all these, he stuck to a tough nationalist, protectionist, anti-immigrant, anti-Muslim and pro-police line. And, as a rank outsider, he defeated 16 talented Republicans. Libertarianism, it turned out, was an ideology with many leaders — Republican senators, governors, think tankers — but very few followers.

A month before the November 2016 election, when everyone expected Trump to lose, Paul Ryan got on a call with other Republican congressmen and told them to feel free to distance themselves from Trump. After the call, the speaker’s approval rating among Republican voters dropped almost 20 points. The base of the party — now older, whiter, and less educated — was with Trump, not Ryan.

Ryan had his faults. He embodied the hypocrisy of Reaganism, advocating fiscal probity while exploding the deficit. He was a bad legislative strategist, unable to repeal Obamacare after years to prepare for it. But he was a genuine and ardent Reaganite. His successors will not be. The second transformation of the Republican Party is now complete.

Fareed Zakaria is a Washington Post Writers Group columnist.