The below sentence appears in the article “Treffen von Trump und Merkel. Muss halt.” from Der Spiegel:
Trump lobt Deutschland länglich als wichtigen Partner im Kampf gegen den Terror und erinnert daran, dass bereits 50 Bundeswehrsoldaten in Afghanistan ums Leben gekommen seien.
As I understand it, the nominative case should be used after als. In the above sentence, however, the adjective wichtig that comes after als seems to be having an ending characteristic of the accusative case (en). Should not the ending of wichtig be in the nominative case (er)?
One more thing: What's the proper English translation of Muss halt (the phrase is part of the article heading)? My version of the translation, Must stop, is not particularly meaningful to me.