“Things fall apart; the center cannot hold; Mere anarchy is loosed upon the world.” It’s time to quote W.B. Yeats’s famous poem again. But this time, it really does seem that the political center is under intense pressure — from left and right — all over the Western world.

In Britain, David Cameron’s center-right government faces a revolt over his country’s membership in the European Union. In Germany, Angela Merkel’s broad left-right coalition is being battered for her handling of migration.

Across Europe, governments that occupy the center ground find themselves struggling against energized ideological movements from right and left.

Centrists are under siege in the United States as well. Hillary Clinton faces the most serious left-wing challenge to a mainstream Democrat in decades. On the Republican side, the moderates have mostly collapsed. The party’s establishment is coalescing around Sen. Marco Rubio (R-Fla.), who, when elected, was described as “the first senator from the tea party.”

The populists and radicals have filled space that the major parties vacated. After the Cold War, political parties in the West started moving to the center — among others, Britain’s Labour Party, the Italian and French socialist parties, and the U.S. Democratic Party. (Geoffrey Wheatcroft writes of the phenomenon in Europe in the National Interest.) The Republican Party is a partial exception to this rule. Yet even there, the last two GOP presidents — the Bushes — governed from the center, certainly enough to enrage their conservative supporters and fuel insurgencies. (George W. Bush’s problems related more to competence than ideology. He did enact a massive tax cut but was a big spender, supported education standards and expanded Medicare.)

Why are centrists so vulnerable? The reality is that these moderate politicians have actually performed well in recent decades. Look at the challenges they have faced: the end of the Cold War, the integration of Eastern Europe, wars in the Balkans, the rise of economic competitors, the Asian economic crisis, 9/11, the global financial crisis. Western governments have steered their countries through these difficult times with skill while maintaining peace, growing economies and adapting to a new technological age.

The problem is that although they may be competent, centrists are dull, practical types. And there is always a search for romance in politics. Even amid centrist success, there are still enough problems to galvanize the romantics who believe the answer is a revolution. For Sen. Bernie Sanders (I-Vt.), it is a revolution from the left; for Sen. Ted Cruz (R-Tex.), it is one from the right; and Donald Trump almost magically mixes and matches the furies of both ends of the spectrum.

David Miliband, former British foreign secretary, remains the most effective spokesman for Europe’s modern center-left. He argues that the left- and right-wing revolts stem from the same force: globalization. “The right has no good answer to the problem that globalization erodes people’s identities. The left has no good answer to the problem that it exacerbates inequality,” he told me. That leaves traditional politicians struggling to hold on to their supporters while outsiders promise easy answers. “The best lack all conviction,” Yeats wrote, “while the worst are full of passionate intensity.”

The simple solutions are, of course, non-solutions. And they mostly won’t happen. We will not build a wall, nor deport 11 million people, nor place a ban on all Muslims entering the United States. Britain will not leave the European Union. (Even if it voted to leave, this would only begin a complicated negotiation with the E.U. that would result in a new arrangement, much as has happened with the Danes and the Irish.) And the E.U. will not crumble because a few countries put up borders to stop migrants and refugees from entering their lands.

But what is happening is political paralysis. The radicals and romantics might not have the power to overturn the centrist consensus, but they can place it under relentless pressure. Cameron will spend the next months consumed with opposing the forces of the “Brexit.” In the United States, the country and its political leaders have spent months debating fantasies. Meanwhile, there is no discussion of the important issues and the actual, plausible policy options to deal with them — regarding the global economic slowdown, massive infrastructure deficits, growing inequality and climate change, among others.

Yeats was wrong. The center can and does hold, but just barely.

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