Reports Ad Age.
How can there be such a disparity?! Even if he minimizes the value of advertising and puts most of his faith in free media — funny that the Trump-hating media won't just cut him off — shouldn't he do a little more advertising than that?
There's the theory that he's saving it all up for October. The ads aren't booked yet, but they are coming. And the Hillary campaign doesn't know where they are coming, what the electoral-college strategy will be when it comes down to the end and what particular issues will be targeted to those states. All that will matter in the end is who can tip those last few states.
I like to look at the "winding path to 270 electoral votes" graphic at FiveThirtyEight — partly because I'm fascinated by the resemblance to intestines...
... but mostly because it shows so vividly how focused the fight really is. Will Trump suddenly dump money in one of the slightly less obvious states like Wisconsin or Virginia, going big on some targeted issue that will catch Clinton flat-footed? That can be done, and it will be a demonstration of Trump's self-vaunted flexibility.
The big disparity Ad Age points to is in booked ads. That money is already committed and Trump's campaign can see where it is. The withholding of money on the Trump side is so extreme. It should be quite alarming to the Clinton side.