The State Department did not respond to requests for comment. But a Foreign Affairs Committee staff member said that the department’s Bureau of Diplomatic Security, whose agents protect diplomats and investigate certain crimes, had told the committee that it would immediately open an investigation.

In the interview with The New York Times, Mr. Parnas said that he had nothing to do with any potential surveillance of Ms. Yovanovitch, and that he doubted it had actually occurred.

“I never took Mr. Hyde seriously,” Mr. Parnas said.

Mr. Parnas said he met Mr. Hyde at the Trump Hotel Washington, where both men were frequent guests. Mr. Hyde also became a fixture at some of the same Republican fund-raising events in Washington and in Florida that Mr. Parnas attended, including the 2019 inauguration of Florida’s governor, Ron DeSantis.

Mr. Hyde, who was often spotted buying rounds of drinks for fellow supporters of Mr. Trump at the Washington hotel, gained access to the Republican events in part because he had donated $25,000 to Mr. Trump’s inaugural committee, a person briefed on the matter said. Republican fund-raising officials viewed him as a prospective donor to America First Action, a pro-Trump super PAC, although he ultimately donated only $1,000, the person said.

In recent years, according to campaign finance records, Mr. Hyde has made tens of thousands of dollars in contributions to various Republican causes, including Mr. Trump’s campaign and the campaign of Representative Greg Pence of Indiana, the brother of Vice President Mike Pence.

Mr. Hyde’s campaign website says that he served in the Marine Corps for eight years, performing security services, including in Iraq after the terrorist attacks of Sept. 11, 2001. His LinkedIn page says that he ran a landscaping and construction company near Hartford, Conn., from 2002 to 2018.

Mr. Hyde’s LinkedIn profile also describes him as a self-employed “change agent” since January 2014. In late 2018, according to his page, he started a government and public relations firm. The home page of the company, Finley Hyde & Associates — Finley is Mr. Hyde’s middle name — has pictures of him with Mr. Trump and the vice president. His campaign website also features a picture of him with Mr. Trump.