It’s possible we are at the beginning of another political recalibration based on national identity. Already center-right parties in Japan and Russia and Israel have lurched in a nationalist direction. And where nationalists do not enjoy outright control, as in Hungary and Poland, they split the center-right coalition, as in France, the U.K., and Germany.

The tendency in Washington is not to take Donald Trump seriously. To describe him as a clown, as someone who will drop out, as someone whose beliefs are non-ideological. I believe that to dismiss him is a mistake. Since declaring his candidacy in June, Trump has been consistent on issues of immigration and trade and security. He has not deviated from building a wall on the southern border, slapping tariffs on imports, criticizing the 2003 Iraq war, praising Vladimir Putin, describing Ukraine as Germany’s problem not ours, and saying Middle East peace depends on Israeli concessions.

Trump’s nationalism has far more in common with the conservatism of Marine Le Pen, leader of France’s National Front, than with the conservatism of Ronald Reagan. Support for a “Muslim ban” is par for the course among European nationalists—by calling for it here all Trump has done is confirm how closely American politics resembles European politics. Reagan was an immigration advocate who signed the 1986 amnesty law.

Indeed, Republican nominees since Ronald Reagan have been internationalist in outlook. They have been pro-free trade and pro-immigration, have supported American leadership in global institutions, and have argued for market solutions and traditional values. A Republican Party under Donald Trump would broadly reject this attitude. It would emphasize protection in all its forms—immigration restriction, trade duties, a fortress America approach to international relations, and activist government to address health care and veterans’ care.