Consider Trump’s core campaign message, from which he rarely wavered. Free trade is bad, and is responsible for the nation’s economic decline. Immigration is an existential threat to the American way of life. Global institutions, treaties, and alliances should be viewed with suspicion. Nationalism is a bulwark against globalization.Of course, Republicans refused to join the League of Nations, and they opposed any involvement in European or Asian wars down to 1941. Anti-globalism remained at the core of Republican beliefs until 1952, when the internationalist Eisenhower became the candidate; the first strong free-trader to get the Republican nomination was Goldwater in 1964.
All of this seems heretical to today’s free-market, foreign affairs conservatives, but it’s actually just the revival of what once passed for party orthodoxy. In the 1920s, Republicans hated free trade, preferring protective tariffs. . . .
Republican suspicion of free trade found a corollary in suspicion of the open borders. Earlier in the 20th century, Republicans had fallen under the spell of writers like Madison Grant, whose polemical 1916 book, "The Passing of the Great Race," argued that the white Anglo-Saxon population would be inundated by the waves of “inferior” groups – Jews, Asians and other non “Nordic” peoples – unless immigration could be curtailed.
Eventually, Republicans in Congress put a stop to immigration, imposing a draconian quota system.
This fits with what I have been trying to say: that until Trump there was no real conservative party in America, and hadn't been since before Reagan or even Goldwater. Many Americans still long to wall off the world and keep things here just as they are, and the whole elite keeps telling them that what they want is impossible. Until Trump.