Center-left political analysts want to believe that economic stagnation and income inequality form the heart of the contemporary populist surge, but the evidence does not bear this out.
In Britain, the pro-Brexit campaigners' shift of focus from economics to immigration and sovereignty proved decisive. Immigration did more than any other issue to put Donald Trump over the top. German Chancellor Angela Merkel's decision to admit more than 1 million refugees from the Middle East sparked the Alternative for Democracy's rise to its new-found status as the country's leading opposition party. Hungarian Prime Minister Viktor Orban's refusal to comply with the European Union's mandated quota of refugees moved his "illiberal democracy" to center stage throughout central and eastern Europe. Most recently, the League's virulently anti-immigrant stance propelled the party from 4 percent of the vote in 2013 to dominant status in right-wing Italian politics. The success of anti-immigrant populism is forcing traditional center-right parties throughout Europe to shift toward these insurgents.
The immigration issue is poisoning democratic politics, and not just in the United States. Purging this poison means resisting the urge to demonize the critics of current policies and instead searching for common ground that promotes the common good. While prejudice and hatred cannot be tolerated, liberals and progressives need to pay more attention to grievances - such as fears about economic and cultural displacement, the rule of law and loss of sovereignty - that should not be dismissed as pure bigotry.
The rise of populism calls on the defenders of liberal democracy to distinguish more rigorously between policy disputes and regime-level threats. Political leaders can assert the right of their nations to put their interests first without threatening liberal democratic institutions and norms. This is a policy dispute within liberal democracy, not about liberal democracy. In a similar vein, the defenders of liberal democracy should acknowledge that control of borders is an attribute of national sovereignty and that liberal democratic citizens can have a wide range of views on the appropriate number and type of immigrants. Protecting liberal democracy against populist threats to individual rights, constitutional checks, and the rule of law does not require defending every detail of every policy that populist parties attack.
Put into practice, this distinction would create political space for a long-overdue resolution of the immigration debate in the United States.
There is no reason for the United States to slash annual immigration by more than 40 percent, as the Trump administration's proposal would do.
The growth of the U.S. labor force has slowed sharply, from nearly 1.5 percent annually in the 1990s to a projected 0.4 percent in the coming decades. Unless we want slower economic growth and an ever-rising ratio of retirees to prime-age workers, we should reject proposals that would slash the overall flow of immigrants into the country.
The case for changing the mix of immigrants is stronger. No other country devotes two-thirds of its annual immigration flow to family reunification. Shifting towards economic contribution as the main criterion for admission, as Canada has done, would make sense politically as well as economically. Although Canada's annual immigration as a share of its population is three times as high as in the United States, its system enjoys super-majority support.
Other changes - an increased focus on the rapid acquisition of English fluency and a working knowledge of American history and civic institutions, for example - would address cultural fears. Acknowledging the legitimacy of widespread concerns about the rule of law through stepped-up enforcement at the border and the workplace would ease the way for a reasonable and humane approach to the millions of immigrants who are present illegally in the United States.
In many Western democracies, the rise of populism has coincided with the collapse of traditional center-left parties, as working-class voters shift their allegiance. In the United States, Democratic Party strategists debate whether regaining the support of these voters would come at too high a price and that the best hope for the future lies in the coalition of minority groups and educated professionals.
But liberal democracy cannot be healthy if groups of embittered citizens are left with no alternative to irresponsible appeals. A reasonable settlement of the immigration issue would put us on a better course.
William A. Galston is senior fellow in Governance Studies at the Brookings Institution and the author of "Anti-Pluralism: The Populist Threat to Liberal Democracy."