Why do you think Clinton's got this in the bag? She's leading by 3-4 percentage points in both national and most swing-state polls[1], which is less than the movement we've seen in the past month. And 15-20% of voters are undecided or third-party right now, significantly increasing the volatility of the polls. FiveThiryEight's analysis[2], which I think is quite thorough, gives Clinton a ~70% chance of winning. Far from "in the bag".
Elections are now won by GOTV efforts. Boots on the ground, volunteers, doorbelling, phone banking, etc.
Whereas Clinton has the 2nd most sophisticated operation in history, Trump doesn't have anything that remotely resembles a campaign, much less an effective GOTV effort.
[1] Specifically, weighted (by sample size) averages of such polls. [2] http://projects.fivethirtyeight.com/2016-election-forecast/