Hungary’s reputation as the troublemaker of Europe will be burnished on Wednesday as its parliament begins debating a contentious issue: whether to give Finland and Sweden the green light to join NATO. Along with Turkey, Hungary has yet to ratify the applications of Finland and Sweden to join the transatlantic defense alliance more than eight months after NATO leaders signed off on their membership bid at a summit in Madrid. Máté Kocsis, head of Orbán’s nationalist Fidesz party caucus in parliament, said last week that a “serious debate” had now emerged over the accession of the two countries. Hungary now...