The evolution of the Republican Party in the past several months has been breathtaking to witness. The party of Reagan is now deeply suspicious of free trade and security alliances while growing ever more fond of Russian autocrat Vladimir Putin. Policy positions, especially in trade and foreign policy, have flipped with such extraordinary speed that it seems like there must be some core instability in the party, a will to power that has shattered any foundational principles. 

That may be true. But the party's rapid abandonment of long-held principles has been possible in large part because it draws on the right's deeper history, a history that reaches back before the Cold War to a nascent conservative movement. That movement grew not out of McCarthyism but an inward-looking nationalism, one that has re-emerged with Donald Trump. 

The story of modern American conservatism cannot be understood without first understanding the America First Committee, the short-lived anti-interventionist movement founded in 1940. Its members ran the ideological spectrum – socialists, progressives, conservatives, fascists – but the AFC drew most of its membership from around Chicago, where conservative nationalism flourished in the 1940s and 1950s.

The AFC dissolved after the attack on Pearl Harbor, but a few years later a number of its members reconvened in Chicago to help launch "Human Events," which would become an influential conservative newsweekly. "Human Events" was sharply out of touch with the prevailing foreign policy preferences of the mid-1940s, especially when the editors made the case for an easy peace with Germany. Indeed, the editors fielded numerous complaints from readers who felt "Human Events" was too sympathetic to Germany, leading them to moderate their coverage.

Conservative nationalists in the 1940s and 1950s fretted about the U.S. becoming too involved in the postwar world, offering an alternative to Henry Luce's call for an American Century, one with the U.S. as the world leader. They worried that the U.S. would sacrifice its sovereignty if it became too entangled in international governance, that it would lose its ability to act unilaterally. ...