But these results may not be as contradictory as they seem. Populism, research suggests, has been steadily growing since the 1960s. It is now reaching a size that is often too small to win outright, but is large enough to shape and, at times, to upend the politics of a country.

Whether populist parties win or lose depends not just on the level of popular support — which appears surprisingly consistent across countries — but also on the nature of the political system.

Western populism may be entering something like its awkward teenage years — able to borrow the car but not own it, have an influence on the household but be too young to run it.

Still, research suggests it will continue growing as a political force. Four major elections from the past year show how this dynamic can play out in different ways.