There's plenty of evidence to suggest that, in the sense of things we would be more likely to see if it were the case than if it weren't. Many things from the Snowden docs; parallel construction; statements of congresspeople and courts that they were unaware or misinformed; Clapper flat out lying to Congress and not facing any charges... Nevertheless, I actually don't think it is the case that we are currently in that position; I am just nowhere near as confident of that as I would prefer to be.
I wouldn't have considered many actions over the course of years by a well positioned bad actor "one step", but if you would then I grant you that wording - I may have been thinking you meant smaller "steps" than you did. I would be tremendously surprised if we were a single action away (though "single precipitating action", less surprised).
I really don't see how you can assert that the things I listed aren't more likely in an environment where those holding power in secret are extending and exercising that power, than in an environment where they are not, which is what it means to be evidence.