Defying his notorious stinginess, Donald Trump more than doubled his campaign spending last month.
Trump burned through roughly $US70 million ($A92 million) as his standing in polls and among fellow Republicans dropped.
Hillary Clinton, spent even more - almost $US83 million.
New reports filed with the Federal Election Commission outline their dramatically different approaches.
Trump, while putting more money than ever into advertising, spent a fraction of the roughly $US66 million Clinton poured into media buys.
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Clinton's payroll topped 800 people, coming in as her second-highest expense of the month, about $US5.5 million.
Trump paid roughly 350 employees and consultants. He has outsourced most of his on-the-ground voter contact to the Republican Party.
The New York real estate mogul has bragged until recently about his low-cost campaign and dismissed the need for television ads and polling services. But in September, he paid $US23 million for commercials.
Perhaps a reflection of his newest campaign manager, pollster Kellyanne Conway, Trump appears to have a new interest in polling.
In August he paid Conway's The Polling Company $US130,000. Last month, he almost tripled his payment to her company, part of $US1.7 million in September expenditures to five different polling firms.
One of Clinton's expenditures causes a double-take.
Her campaign reimbursed employees who purchased $US260 worth of products from Trump International Hotel in New York.
That was for props - a tie, polo shirt and hat - in a Clinton campaign digital video highlighting that Trump doesn't make all of his products in America.
Indeed, the Clinton campaign line-item in the fundraising report reads: "Merchandise Not Made In America."
September was the best fundraising month for both candidates. Of the $US100 million Trump said he raised for his presidential bid and his Republican partners, about $US55 million went to his campaign.
Clinton's campaign said she raised $US154 million, and her September filing showed about $US74 million of that ended up in her campaign account.
