The nomination process is highly structured for the constituency candidates. There are delegate conferences within each party to choose the constituency candidate. There are legal prescriptions that a party must follow in order to set up the list, which is a kind of hierarchical system. It starts at the bottom. There are small delegate conferences of party delegates, then some of them meet at a higher level because the party lists in Germany are state lists. All of this must be properly documented and be submitted to the federal election authority in order to be admitted to run in the election.
On August 31st, 2016. See this statement in context.