Donald Tusk recently returned to Brussels as a “proud Pole” and a “proud European.” It is not quite clear which ascription comes first. Equally unclear is the capacity in which Mr. Tusk voyaged, for he is not yet Poland’s prime minister. Yet what is clear is that should Mr. Tusk assume the role, Poland could well see “more Paris in Warsaw,” as Mr. Tusk told President Macron of France last year — and likely not the good parts.