Because he has mentioned it since 2012.
As I understand it Duncan Hunter’s San Diego border fence has been about as effective as any physical barrier can be. Granted it doesn’t carry the magical properties it would have if we called it a wall but its still effective at doing its job.
No he hasn’t, he has only mentioned the stupid fence, only one candidate has campaigned for a wall and truly secure border as they have in Israel. In fact, Cruz wasn’t even talking about stopping amnesty and immigration until Trump force fed it to him and the other candidates.