WASHINGTON—The fund paying legal fees for President Trump’s associates ensnared in the Russia investigation raised about $150,000 in the third quarter of 2018, a drop from the previous period, according to a new tax filing.

Nearly the entirety of Patriot Legal Expense Fund Trust’s receipts between July and October came from Anthony Lomangino, a recycling industry titan and member of Mr. Trump’s Mar-a-Lago resort in Florida. Mr. Lomangino gave the fund $50,000 in July and another $100,000 in late September.

California...