Mysterious outside groups are asking state parties for personal data on potential delegates, Republican campaigns are drawing up plans to send loyal representatives to obscure local conventions, and party officials are dusting off rule books to brush up on a process that hasn’t mattered for decades. As Donald Trump and Ted Cruz divide up the first primaries and center-right Republicans tear one another apart in a race to be the mainstream alternative, Republicans are waging a shadow primary for control of delegates in anticipation of what one senior party official called “the white whale of politicsâ€: a contested national convention.