President Trump and his most devoted allies (both in Congress and on cable news) have themselves all worked up once again.In a matter of days, a conspiracy theory has once again become mainstream thought on the American right. The assertion this time is, very roughly, that the Deep State embedded a saboteur in the Trump campaign’s early days. It could be, per the president’s Twitter feed, “one of the biggest political scandals in history.”It is not “one of the biggest political scandals in history.”