Hillary is spending millions to preserve what seems in many polls to be a small lead. Trump is spending very little.
I’m guessing this is not missed on the Hillary camp.
I would suspect that at some point Trump will start spending money on advertising and by the time he does Hillary will have had to show many of her best cards as well as spent a lot of her available resources.
In prior presidential elections the GOP would run out of money (or whatever they did with it) For at least a month before election and the Democrats flooded the airwaves with nothing coming from our side. I do believe this is where and when Trump is going to hit them and hard. They’re not used to having competition during that time.