Michael Caputo last week did what has become a rite of passage for former Trump campaign aides.

He traveled to Washington to sit down for a Russia collusion grilling by staffers for special counsel Robert Mueller and the Senate Select Committee on Intelligence.

A number of Trump people have made the tour, but not quite with the flair of the Republican media adviser. With a lawyer at his side and his legal bills threatening his family’s well-being, Mr. Caputo rolled the dice and won.

He released a combative statement that he had read directly to Senate staffers, with Democrats in mind. He accused them of being in cahoots with a former colleague, Daniel J. Jones, who was a close aide to Sen. Dianne Feinstein, California Democrat. Mr. Jones has amassed a huge pot of cash to investigate President Trump and has ties to dossier writer Christopher Steele.

“Forget about all the death threats against my family,” Mr. Caputo said. “I want to know who cost us so much money, who crushed our kids, who forced us out of our home, all because you lost an election. I want to know because God damn you to Hell.”

His outburst struck a chord in Trump land. Mr. Caputo checked his GoFundMe account over the weekend and saw that the pot had swelled to more than $250,000.

“This covers my legal fees, unless it turns into hellish litigation,” Mr. Caputo told The Washington Times. “And the more I speak out, the more likely it is I get dragged along.”

Mr. Jones, who runs the investigative firm Penn Quarter Group, told the FBI last year that he had acquired $50 million from mysterious donors to continue the Trump-Russia investigation.

The partisan opposition research started in June 2016, fueled by cash from the Democratic National Committee and the Hillary Clinton campaign. They paid Fusion GPS, which paid Mr. Steele, the former British spy who produced an unsubstantiated dossier accusing Trump people of Russian collusion.

Mr. Jones has kept part of that team together. He told the FBI that he is paying Fusion GPS and Mr. Steele to keep digging for Russia-Trump dirt.

Mr. Caputo, a brash best friend of Republican strategist Roger Stone, charges that the Jones-Fusion-Steele troika explains some of the continuous Russia conspiracy stories.

The McClatchy news service resurrected the dossier tale that Trump attorney Michael Cohen had traveled to Prague to meet with Kremlin aides and plot a cover-up of Russian hacking of Democratic Party computers. Glenn Simpson, Mr. Steele’s handler at Fusion, suggested in congressional testimony that Mr. Cohen made the trip via a yacht and a Russian airplane.

If true, the trip would prove collusion. There has been no independent verification. Mr. Cohen has denied in sworn congressional testimony, under the threat of a perjury charge, that he ever traveled to Prague.

Asked why he believes Penn Quarter’s Mr. Jones is behind the Prague story and others, Mr. Caputo said, “I know because it’s a new day in journalism. Not only do they write false stories, they’re not so shy about gossiping about their sources either.”

Mr. Caputo accused intelligence staffers point-blank of working with Mr. Jones. His scenario: Mr. Jones meets with the FBI, gives it his opposition research and then sells a story that the special counsel has evidence that Mr. Cohen traveled to Prague.

“That’s your pal Dan, isn’t it?” Mr. Caputo told Democratic staffers. “He came up with some kind of hollow proof that Michael Cohen was in Prague meeting with Russians when he wasn’t. He tried to sell that to reporters, and they didn’t buy it because it doesn’t check out. So, to get a reporter to write up his line of bull, he gave the documents to the office of special counsel. We know that’s likely, because he’s told people he’s briefing investigators.”

Penn Quarter did not return messages sent to the company’s email address.

Mr. Jones‘ $50 million anti-Trump fund was disclosed in the recent Republican majority report on Russia by the House Permanent Select Committee on Intelligence. The panel acquired the FBI’s March 28, 2017, interview report, or 302, on Mr. Jones. He said he planned to share his dirt with the news media, the FBI and congressional committees, which presumedly would include the Senate intelligence panel.

Mr. Jones‘ name surfaced in private text messages between Sen. Mark R. Warner, Virginia Democrat and Senate intelligence committee vice chairman, and a lobbyist for Russian oligarch Oleg Deripaska.

Mr. Warner last year was trying to secure a committee interview with Mr. Steele and viewed the lobbyist as a go-between. The lobbyist told Mr. Warner that Mr. Steele was talking to Mr. Jones. The lobbyist quoted Mr. Steele as saying that Mr. Jones had a planned meeting with Mr. Warner, according to text messages acquired by Fox News.

A spokesman for Mr. Warner did not return a message seeking comment.

Mr. Caputo’s risk-taking was not confined to his explosive statement. He did a cable TV news tour knowing he might irk a Mueller prosecution staff dominated by Democratic Party donors.

“Investigators know I need help with my legal fees, and they know how to use that against you,” Mr. Caputo told The Times. “After this unexpected grass-roots support from 5,000 donors of less than $50 each, investigators also know the [Make America Great Again] team’s got my back. And I’m not so scared anymore.”

Mr. Caputo declined to discuss specifics in his Mueller sit-down.

Logic says he was asked about his friend, Mr. Stone, a longtime political adviser to Mr. Trump who in 2015 helped forge an emerging presidential campaign at Trump Tower. Mr. Stone left the campaign in August 2015. Mr. Caputo served on the campaign from November 2015 to June 2016.

Mr. Stone communicated, via Twitter direct message, with a Russian hacker posing as the international hacker “Guccifer 2.0.” Mr. Stone also emailed a colleague and told him he planned to dine with Julian Assange, who runs WikiLeaks, which published the stolen Democratic Party emails.

Mr. Stone has said his conversation with Guccifer 2.0 was innocuous. He wrote a story for Breitbart saying the real hacker was Guccifer 2.0, not the Russians.

Mr. Assange is living under diplomatic protection in the Ecuadorean Embassy in London. Mr. Stone said his bragging of a pending dinner was a flip attempt at humor. He said he has never met with or spoken to Mr. Assange.

Asked about his Mueller testimony, Mr. Caputo said: “The good news for the American people is this investigation is moving forward resolutely. The bad news is they are focused on bogus allegations of Russian collusion.”