LONDON – Sixty-five years ago, what has become the European Union was an embryo conceived in fear. It has been stealthily advanced from an economic to a political project, and it remains enveloped in a watery utopianism even as it becomes more dystopian. The EU’s economic stagnation – in some of the 28 member nations, youth unemployment approaches 50 percent – is exacerbated by its regulatory itch and the self-inflicted wound of the euro, a common currency for radically dissimilar nations. The EU is floundering amid mass migration, the greatest threat to Europe’s domestic tranquility since 1945.

The EU’s British enthusiasts, who actually are notably unenthusiastic, hope fear will move voters to affirm Britain’s membership in this increasingly ramshackle and acrimonious association. A June 23 referendum will decide whether “Brexit” – Britain’s exit – occurs. Americans should pay close attention because this debate concerns matters germane to their present and future.

The EU is the linear descendant of institution-building begun by people for whom European history seemed to be less Chartres and Shakespeare than the Somme and the Holocaust. After two world wars, or a 31-year war (1914-45), European statesmen were terrified of Europeans. Under the leadership of two Frenchmen, Robert Schuman and Jean Monnet, they created, in 1951, the European Coal and Steel Community to put essential elements of industrial war under multinational control.

This begat, in 1957, the European Economic Community, aka the Common Market. Money, said Emerson, is the prose of life. The EU is the culmination of a grand attempt to drain Europe of grandeur, to make it permanently peaceful by making it prosaic – preoccupied and tranquilized by commerce. European unity has always been a surreptitious political project couched in economic categories.

Britain’s Remain side is timid and materialistic, saying little that is inspiring about remaining but much that is supposedly scary about leaving. The Leave campaign is salted with the revolt-against-elites spirit now fermenting in nations on both sides of the Atlantic. The Remain camp relies heavily on dire predictions of economic wreckage that would follow Brexit – forecasts from the U.K. Treasury, the International Monetary Fund, the Organization for Economic Cooperation and Development, etc.

Although none of these, in spring 2008, foresaw the crisis of autumn 2008, they now predict, with remarkable precision, economic damage to Britain’s economy, the world’s fifth-largest, if it is detached from the stagnation of the EU. For example, the U.K. Treasury projects that Brexit would cost Britain 6.2 percent of GDP by 2030. This confirms the axiom that economists prove their sense of humor by using decimal points.

Passion is disproportionately on the Leave side, which is why a low turnout will favor Brexit: Leavers are most likely to vote. Current polls show Remain slightly ahead, but Leave has a majority among persons over age 43, who also are most likely to vote.

The most conspicuous campaigner for Brexit is Boris Johnson, the two-term Conservative former mayor of London. He is an acquired taste, and some thoughtful people oppose Brexit because, if it happens, Prime Minister David Cameron, who leads the Remain campaign, might be replaced by Johnson.

Johnson is frequently compared to Donald Trump. However, Johnson’s only real resemblance to Trump, other than an odd mop of blond hair, is a penchant for flamboyant pronouncements, as when he said that Barack Obama opposes Brexit because Obama’s Kenyan background somehow disposes him against Britain.

Actually, Obama likes the European Union’s approximation of American progressives’ aspirations. These include unaccountable administrators issuing diktats and what one EU critic calls “trickle-down postmodernism” – the erasure of national traditions and other impediments to “harmonizing” homogenized nations for the convenience of administrators.

Brexit might spread a benign infection, prompting similar reassertions of national sovereignty by other EU members. Hence, June 23 is the most important European vote since 1945.