WASHINGTON — During the summer of 2018, as Richard Seddon, a former British spy, was trying to launch a new venture to use undercover agents to infiltrate progressive groups, Democratic campaigns and other opponents of President Donald J. Trump, he turned for help to a longtime friend and former colleague: Erik Prince, the private military contractor.

Mr. Prince took on the role of celebrity pitchman, according to interviews and documents, raising money for Mr. Seddon’s spying operation, which was aimed at gathering dirt that could discredit politicians and activists in several states. After Mr. Prince and Mr. Seddon met in August 2018 with Susan Gore, a Wyoming heiress to the Gore-Tex fortune, Ms. Gore became the project’s main benefactor.

Mr. Prince’s role in the effort, which has not been previously disclosed, sheds further light on how a group of ultraconservative Republicans employed spycraft to try to manipulate the American political landscape. Mr. Prince — a former C.I.A. contractor who is best known as the founder of the private military firm Blackwater and whose sister, Betsy DeVos, was Mr. Trump’s education secretary — has drawn scrutiny over the years for Blackwater’s record of violence around the world and his subsequent ventures training and arming foreign forces.

His willingness to support Mr. Seddon’s operation is fresh evidence of his engagement in political espionage projects at home during a period when he was an informal adviser to Trump administration officials.

Mr. Seddon’s recruitment of Mr. Prince to help him secure funding is just one of the new details about Mr. Seddon’s operation revealed in documents obtained by The Times and interviews with people familiar with his plans. They provide additional insight into the ambition of the operation to use undercover operatives to target Republicans seen as insufficiently conservative, as well as to, as one document describes it, “research, penetrate and infiltrate the radical left networks.”

The Times previously reported that, in 2016 and 2017, Mr. Prince recruited Mr. Seddon to join the conservative group Project Veritas to teach espionage skills to its operatives and manage its undercover operations. Mr. Prince also allowed Project Veritas to use his family’s Wyoming ranch for training. Mr. Seddon launched his privately funded spying effort after leaving Project Veritas in 2018.

It is unclear how many potential donors Mr. Prince might have approached for money for Mr. Seddon’s venture besides Ms. Gore. Separately, Ms. Gore unsuccessfully tried to raise money for the project from Foster Friess, a billionaire Wyoming businessman, during a January 2019 meeting, three people said.

During the 2018 meeting with Ms. Gore, according to one person familiar with it, Mr. Prince and Mr. Seddon said the goal of the private spying operation was to gather dirt both on Democrats and “RINOs” — slang in conservative circles for “Republicans in name only.” The plan was to begin in Wyoming, they said, and expand operations from there.

Over two years, Mr. Seddon’s undercover operatives also developed networks in Colorado and Arizona, and made thousands of dollars in campaign donations posing as Democrats, both to the Democratic National Committee and individual campaigns. Funneling money surreptitiously to campaigns through other donors — known as straw man donations — would violate federal campaign finance laws.

Mr. Prince is separately under investigation by the Justice Department on unrelated matters, according to people familiar with the case. The scope of that investigation is unclear.

Mr. Prince declined to comment. Mr. Seddon and Ms. Gore did not respond to messages.

The documents give new details about efforts to manipulate the politics of Wyoming. While the state is currently solidly Republican, Mr. Seddon and Ms. Gore believed it was in danger of turning toward the Democrats, as Colorado has.

One target in particular was Gov. Mark Gordon, who was viewed as a RINO in some Wyoming conservative circles.

After Mr. Gordon won a close Republican primary battle against Mr. Friess, the billionaire, in August 2018, Mr. Friess blamed his loss on Democrats switching parties on Election Day to vote for Mr. Gordon.

“It seems like the Democrats have figured out this party switch deal to their advantage,” Mr. Friess wrote in an email obtained by Wyofile, a political news site in Wyoming. He added, “With Trump getting 70 percent of the vote, it shows how the Democrats have been able to control our elections with putting on a Republican coat.”

Mr. Gordon took office in January 2019. A document that month said that Mr. Seddon’s operatives had “identified three potential sources in the new governor’s administration and have begun accelerated cultivations with a view to early recruitment.”

Later in January, the operatives wrote that they had “successfully recruited another source with a role in the new governor’s administration,” adding that the “source has agreed to provide insights, help expose corruption and assist with eventual placement of undercovers.”

According to the documents, Mr. Seddon’s operatives also aimed to dig up information on Steve Harshman, the Republican speaker of the House in Wyoming at the time, who was also seen by some conservatives as not sufficiently supportive of Mr. Trump. One February 2019 report said that a “new undercover will be joining the team” and tasked with targeting Mr. Harshman.

Months later, in June 2019, a report said “we are expecting a big haul, including new lines of intelligence on the Republican side of the house.”

The documents also show that, beyond Ms. Gore, other prominent Republicans in Wyoming were involved in Mr. Seddon’s spying operation.

One of the documents indicates that Marti Halverson, a former Wyoming state lawmaker, provided a list of people for the operatives to target. The list included John Cox, then the director of Wyoming Department of Workforce Services, and Scott Talbott, then the director of the Wyoming Game and Fish Department. The document is dated December 2018 and said that Mr. Talbott was “another of the names of corrupt individuals from Marti.”

Reached by phone, Ms. Halverson said: “Frankly, I have nothing to say on the subject.” She then hung up.

Mr. Seddon used other former Project Veritas employees to help with the Wyoming operation, including James Artherton, a British operative code-named “kimchi” who was involved in a Project Veritas plan targeting an editor for The New York Times in London in 2017.

One of the undercover operatives also got a job working for a consortium of wealthy liberal donors — the Wyoming Investor Network — which had made a strategic decision to support Republican moderate candidates over those more closely aligned with Mr. Trump’s agenda, the documents say. The job put her in a position to gain valuable information about which Republican candidates the group was supporting with independent advertising.

Mr. Prince has previously been involved in trying to find dirt on Democratic politicians. In 2016, Republican operatives believed they had obtained deleted Hillary Clinton emails from the dark web, and sought Mr. Prince’s assistance to authenticate them, an episode investigated by Robert S. Mueller III, the special counsel in the Trump-era Russia inquiry.

The special counsel’s report said that Mr. Prince “provided funding to hire a tech adviser to ascertain the authenticity of the emails. According to Prince, the tech adviser determined that the emails were not authentic.”

Later that year, Mr. Prince turned to Mr. Seddon to help train the Project Veritas operatives. The two men had known each other since Mr. Prince’s days running Blackwater, and shared an affinity for guns and the American West. Mr. Seddon owns a cabin that he keeps stocked with guns, food and other supplies as preparation for a cataclysmic event in the United States.

During a meeting in a Las Vegas suburb last April of employees of Ms. Gore’s organization, the Wyoming Liberty Group, Mr. Seddon pitched a proposal to build a website where other so-called preppers could buy their own supplies and communicate with each other in the event of what he called a “Black Swan” moment — a major terrorist attack, another pandemic or a civil war.

Ms. Gore ended up rejecting the proposal because it was too expensive — people with knowledge of the plan said it would start in the hundreds of thousands of dollars.