In the United States presidential election, Mr. Trump’s populist method for winning the election may propel populist-style parties to emerge in Europe and other parts of the world. We must keep a watch out for and be alert to the negative sides of populism.

Populism is a political approach that seeks to gain power by using the good favor, discontent and fears of ordinary people to create confrontation against an existing system of elites.

In the presidential election, Mr. Trump made an appeal saying he, himself, was an outsider of the existing ruling class. He drummed up support by stirring up the white middle class, who are angry about widening disparity and anxious about the increasing number of immigrants in the U.S. This is textbook populism.

For Americans suffering from these strains in society, it is perfectly natural to revolt against the existing class of elites who will do nothing to alleviate their suffering. And sometimes, that can be the impetus for honest societal change.

However, the problem with populism is it often conflates and expands negative energies within a society — such as class consciousness and bigoted nationalism. Mr. Trump combined divisive rhetoric with misinformation to incite voters.

As this populist tide moves along, views get distorted and democracy itself deteriorates. Minorities are oppressed, and societal divisions deepen. The side effects of this are huge and without end.

In a June referendum in the United Kingdom, supporters of leaving the European Union won, but it was pointed out that politicians in favor of leaving the EU garnered support by making campaign pledges based on a large amount of misinformation. In Europe, where the influx of immigrants is causing societal issues, there is an increase in energy behind extreme right parties and EU skeptics who both advance a policy rejecting immigrants. A large number of these political parties are welcoming Mr. Trump’s victory.

In Japan as well, a politician recently made a comment that seemed to defend a riot police officer who shouted dojin (savage) at protesters of U.S. military bases in Okinawa. Tendencies toward allowing divisive statements foster populism.

In order to turn the legitimate rage of the people into energy for positive societal change, self-searching and self-reform is needed from the existing political parties and politicians. The only way is to walk among the ordinary people whose voices are rarely heard, and start building down-to-earth solutions while understanding their troubles. Anything short of that, and the wave of populism will crash down onto society.