Populism's rise has sparked fundamental questions for advanced democracies around the world.

Perhaps the biggest question is why it's happening. Some research points to economic explanations. Americans who gravitated to President Trump's nationalistic appeals and British voters who approved leaving the European Union were frustrated by job losses associated with globalization. And that anxiety made them susceptible to politicians who promised to claw back their economic power.

Political scientist Yotam Margalit says that explanation is overstated. He says that long-term cultural changes, like growing ethnic diversity and the shift toward urbanization, are bigger factors underlying the populist appeal.

These changes have sparked resentments among some groups that threaten to undermine liberal democracy, itself.