Democratic presidential candidate Hillary Clinton arrives in Washington on Saturday. (Photo by Melina Mara/The Washington Post)

This post has been updated.

The massive investment that Democratic presidential nominee Hillary Clinton is making on the airwaves dominated her spending in August, as her campaign plowed more than $33 million in ad production and airtime, a new campaign finance filing shows.

Clinton's media expenses accounted for 68 percent of the $49 million that her campaign raced through in its biggest spending month yet. She doled out $5 million to pay 789 staffers in August. And she dramatically upped her polling, shelling out almost $1.3 million to five separate firms, up from $244,173 in July.

The former secretary of state still ended the month with more than $68 million in the bank, thanks to her record-breaking fundraising in August. She collected $62.5 million for her campaign and $81 million for the Democratic National Committee and state parties, thanks to high-dollar fundraisers she headlined around the country.

As Clinton was gathering those large checks, her small donations dropped, compared with the previous month. In August, contributions of $200 and less to her campaign totaled $17 million, down from $24 million in July, when both parties held their quadrennial nominating conventions. Officials said that they are on track to have their best online fundraising month in September.

The dip came as GOP nominee Donald Trump saw huge growth in his small-donor base. By August, his campaign had collected contributions from 2.1 million individual donors, closing in on Clinton's 2.3 million donors. About $70 million of the $90 million he raised in conjunction with the Republican National Committee in August were small donations raised online or through direct mail, officials said.