Mr. Futerfas did not respond to a request for comment, nor did representatives from the Trump campaign and Jones Day.

Jones Day also represents the campaign in matters related to election and campaign finance law, as well as litigation stemming from the campaign, and it is not clear what percentage of the legal payments relate to those matters, as opposed to the Russia investigations.

The legal spending revealed on Sunday brings to $2.1 million the legal fees paid by the campaign and its two joint committees this year.

The spending not consumed by legal expenses was more reflective of Mr. Trump’s campaign-style political operation, which did not pause after his election, unlike most presidential campaigns’ operations, which are dialed back or rolled into party committees. Mr. Trump still holds rallies around the country, and the costs included facility rentals, as well as travel and the red Make America Great Again hats sold on Mr. Trump’s campaign website.

The campaign has also continued spending heavily on online fund-raising and other digital outreach, paying $1.1 million in the third quarter to firms run by the campaign’s digital director, Brad Parscale, who also has been interviewed by congressional investigators in Russia inquiries.

Mr. Trump’s campaign and its joint committees with the Republican Party have gotten off to a quick fund-raising start for his 2020 re-election effort, raising a combined $40 million this year. Mr. Trump has headlined big-ticket fund-raisers with major donors, while the campaign also has raised almost $7 million from small donors, partly through an email program with solicitations pegged to news events like Mr. Trump’s feud with National Football League players over their protests during the national anthem.

The Republican National Committee, which discloses its finances to the Federal Election Commission on a different schedule and did not file a report on Sunday, has also paid legal fees related to the Russia inquiries, including to Mr. Futerfas’s firm. It is legally permissible for campaigns and party committees to foot the bill for legal costs that stem from matters related to the campaign in question.