Jay Cost writes on the beginning of the real campaign. According to Cost, the real campaign
Is about persuading voters - who by their own admission are still quite persuadable - in the early states. So, it's about clever television advertisements, solid organizations that can get out the vote, and the campaign message. That is what the real campaign is. It is just now starting. Unfortunately, if you do not live in any of the early states - your access to it is mediated by the press.
That's bad! Cost contrasts the "real campaign" with the "perpetual campaign" in which "both sides constantly endeavor to win the news cycle and attract positive media attention":
The perpetual campaign is not without value. If it was valueless, candidates would not engage in it. The problem for observers like you and me is that the media tends to overestimate the value that the perpetual campaign has - so consumers of the news tend to get a biased, i.e. systematically skewed, view of exactly what is happening. This is not surprising, as the perpetual campaign is largely geared to the media.
It's important to recall this distinction between "perpetual" and "real" campaigns whenever the subject of Clinton's "inevitability" arises. Ultimately, there's one thing that you can be sure may stop Clinton: The voters.