LONDON — He has been depicted as a snarling demagogue in France, equated with Donald Duck in Spain, and described as worse than Lord Voldemort in Britain.

In Europe, the birthplace of the Enlightenment, Donald Trump has been treated variously as a disturbing curiosity or an entertaining political show barker. His nearly every move and pronouncement has been reported from Paris to Berlin to Helsinki, even as commentators on both left and right have dismissed the notion of President Donald J. Trump as the stuff of fantasy, or, at worst, a momentary lapse of reason.

That is changing. With a series of wins in key Republican primary states, and with the billionaire’s expected strong showing when 12 states hold primaries or caucuses on Tuesday, the European media, like its American counterpart, is adjusting to the prospect of a seemingly unstoppable Trump juggernaut. The reaction is a mix of befuddlement, outrage and panic, along with admiration in some unlikely quarters.

And satire. The Spanish newspaper El País recently published an imaginary letter from the grave in which Philip II, a 16th-century Spanish king who ruled a vast empire, offers advice to Mr. Trump. Noting that his nation had also suffered from roguish subjects demanding free handouts, and Muslim terrorists masquerading as peaceful citizens, the king advises Mr. Trump to “consider bringing back the Inquisition.”