BERLIN, Aug 27 (Reuters) - A senior member of Chancellor Angela Merkel's Christian Democrats (CDU) broke ranks with the government over the future of Opel on Thursday, saying Canadian automotive firm Magna is not necessarily the best bidder for the carmaker. "It's of secondary importance who the owner is," Guenther Oettinger, CDU premier of the southern state of Baden-Wuerttemberg, told the Rheinische Post daily.