Clinton Outspending Trump on Ads 10-1

Anyone watching the Olympics from Rio has been seeing a lot of Hillary Clinton, but there have been no Trump sightings during the games. That’s because the Clinton campaign has spent some $14 million on advertising during the games, according to the Associated Press.
In fact, NBC News tells us that since the primary season ended the Clinton campaign has spent $61 million on TV ads, with pro-Clinton PAC’s running an additional $43 million in pro-Hillary ads. The Trump campaign has spent zero dollars. PAC’s supporting Trump have spent just $12.2 million for ads, a drop in the bucket compared with traditional presidential campaigns.
The campaign of the long-shot Green Party candidate, Jill Stein, has spent $189,000 more on TV advertising for the general election than the Republican nominee, Donald Trump. — The Washington Post

Trump raised $82 million in July

It’s not that Trump lacks for money these days. The New York Times reported that Trump and the GOP raised $82 million in July alone. Mr. Trump might not be able to match the $2 billion fundraising goal that the Clinton campaign set in May of 2015, but he has more than enough cash on hand to buy TV spots if he wanted too.
Trump compared himself to “an old race horse” just hanging back to see what happens.
I think we have some pretty good ads but we don't want to go too fast. Just nice and easy. — Donald J. Trump
Trump has gotten $4.3 billion in free media coverage
Trump appears to be following the same strategy that worked well for him during the primaries of using the media to keep him before the public. The New York Times estimated that Mr. Trump received more than $2 billion of free media coverage during the primaries, and all indications suggest that number has continued to grow since the primaries.
"Trump had gotten $4.3 billion in free media in the 12 months through July, according to data provided by MediaQuant — nearly twice Clinton’s total." — Five Thirty Eight

In 2008 the GOP did not hold their Convention until September

Trump appears to be running a “hang back” strategy that will save his money until America returns from its collective summer vacation in the first week of September. Indeed, the 2016 nominating convention was the first election cycle since 2000 that the GOP nominating convention occurred before the end of August and in 2008, it did not happen until the first week of September.
It may be that Trump is waiting for the country to get past Labor Day before he starts a sprint that will take him to Election Day. Whether that strategy will prove to be a winning one, only time will tell.