WASHINGTON – The first domino was an eager Trump campaign operative who shared what sounded at the time like an idle boast that Russia had dirt on Hillary Clinton.

The conversation between George Papadopoulos, a largely unknown foreign policy adviser for Donald Trump’s then-fledgling bid for the White House, and an Australian diplomat took on significance only later, after the Democratic National Committee said Russian hackers had stolen troves of emails. It became the first inkling that “Americans might be working with the Russians,” former FBI Director James Comey would later tell a House committee.

Nearly three years later, the investigation launched from that single contact has taken down a half-dozen senior aides to President Donald Trump, including his campaign chairman Paul Manafort, national security adviser Michael Flynn and personal attorney Michael Cohen. And it has cascaded far beyond that, into Trump's campaign and private business.

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Now, as the White House braces for the imminent delivery of special counsel Robert Mueller's final report on the Russia investigation, Cohen has raised the prospect that virtually no one in Trump’s complicated political and business sphere may be safe from federal scrutiny.

In explosive testimony before a separate House committee on Wednesday, Trump’s former fixer – now a felon and government informant – described a web of federal investigations that have metastasized far beyond Russian interference in the 2016 election to include separate examinations of Trump’s business operations and the roles played by son Donald Trump Jr. and Trump Organization finance chief Allen Weisselberg.

And he accused the president of having participated in a criminal conspiracy.

Trump and his defenders attacked Cohen's credibility, saying there's little reason to trust someone who three months ago pleaded guilty to lying to Congress. But more than the accusations Cohen made in his sworn testimony, his descriptions of the breadth of subjects federal investigators are pursuing could have grave implications for Trump, his family and his business long after Mueller's team departs the scene.

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Rudy Giuliani, the president's lead lead defense attorney, largely dismissed Cohen's testimony as the product of a "tainted witness" whose own convictions related to financial fraud, lying to Congress and campaign finance violations called his credibility into serious question.

"Look, this whole thing started with allegations of collusion with Russia," Giuliani told USA TODAY. "They haven't proved that. All the rest are process crimes that don't involve the president."

While Cohen drew fresh attention during his congressional testimony to hush-money payments to porn star Stormy Daniels, he indicated that Manhattan prosecutors were continuing to review the involvement of Trump Jr. and Weisselberg in that plan to conceal an alleged affair with Trump. The Trump Inaugural Committee also is in the sights of prosecutors in New York, having recently acknowledged receipt of a subpoena seeking information related to possible fundraising irregularities.

And late into Cohen's marathon House testimony Wednesday, after the the former Trump attorney offered a searing account of his dealings with the president, he dropped another stunner in a matter-of-fact exchange with Rep. Raja Krishnamoorthi, D-Ill.

"Is there any other wrongdoing or illegal act that you are aware of regarding Donald Trump that we haven't yet discussed today?" Krishnamoorthi asked.

"Yes," Cohen responded, declining to elaborate because the issue is "currently being looked at by the Southern District of New York," a reference to federal prosecutors in Manhattan.

Links to Russian election interference

The investigation of Russian election interference snowballed into a probe by special counsel Robert Mueller that has so far produced charges against 34 people and three companies.

Among those have been a dozen Russian intelligence officials accused of hacking Democratic political organizations and a handful of onetime top aides to Trump, including former campaign chairman Manafort, his deputy Rick Gates, former national security adviser Flynn, longtime adviser Roger Stone and Cohen.

Mueller’s office has revealed details of Russian efforts to use stolen emails and illicit social media campaigns to help Trump win the White House and a campaign eager to benefit from that activity, but so far prosecutors have alleged no connection between the two.

Cohen told lawmakers that he could not provide one.

"Questions have been raised about whether I know of direct evidence that Mr. Trump or his campaign colluded with Russia," Cohen said. "I do not. I want to be clear. But, I have my suspicions."

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At least some of those suspicions, according to Cohen, were driven by Trump's interest in how the anti-secrecy group WikiLeaks could help his campaign. He said Trump knew in advance that WikiLeaks was planning to release a batch of damaging stolen emails about Hillary Clinton shortly before the convention at which she was to receive the Democratic presidential nomination.

Cohen said he was with Trump when Stone, on a speakerphone in Trump’s office, told the candidate he had spoken to WikiLeaks founder Julian Assange and that “within a couple of days there would be a massive dump of emails that would damage Hillary Clinton's campaign.”

Cohen testified that the conversation happened on July 18 or 19, shortly after federal prosecutors say WikiLeaks obtained stolen emails from an online persona that was a front for the Russian intelligence service that had carried out the hacks. WikiLeaks replied that it would release them “this week,” prosecutors alleged in an indictment.

WikiLeaks said in a statement that Assange had never spoken with Stone, though prosecutors have told a judge that they obtained communications between Stone and the organization.

Cohen said he did not know what emails WikiLeaks planned to release. A week earlier, Assange had said publicly that WikiLeaks planned to reveal additional emails from the private server Clinton maintained while she was secretary of state. Instead, days after the conversation Cohen described, WikiLeaks disclosed thousands of emails stolen from the Democratic National Committee.

That same day, prosecutors allege, an unnamed senior member of Trump’s campaign was “directed” to get in touch with Stone about “additional releases” of Stolen emails, and that Stone later “told the Trump campaign about future releases of damaging material.”

Obstruction of justice

The FBI opened an obstruction of justice investigation into Trump shortly after he fired the bureau’s director, James Comey, in 2017. An FBI lawyer, Cecilia Bessee, told lawmakers in December that the inquiry was ongoing. Prosecutors have revealed nothing about where that review is headed, but they devoted considerable attention to investigating Trump aides – including Flynn, Cohen, Stone and Manafort – who they say lied to the FBI or Congress.

Cohen on Wednesday placed the president squarely at its center. He testified that Trump had implicitly encouraged him to lie to Congress about efforts to build a Moscow high-rise while he was seeking the Republican nomination.

Cohen pleaded guilty last year to falsely telling lawmakers that negotiations over the project, which continued until Trump had wrapped up the Republican nomination, had ended months earlier, in an effort to downplay his boss’ ties with Moscow.

He told Congress on Wednesday that Trump “did not directly tell me to lie to Congress,” but also that the president didn’t have to: “At the same time I was actively negotiating in Russia for him, he would look me in the eye and tell me, there's no Russian business, and then go on to lie to the American people by saying the same thing,” Cohen said. “In his way, he was telling me to lie.”

Cohen said the instruction was not ambiguous: “He doesn't give you questions, he doesn't give you orders, he speaks in a code. And I understand the code because I've been around him for a decade.”

And he testified that some of Trump’s other lawyers, including Jay Sekulow, had reviewed and edited a false written statement before Cohen delivered it to Congress. Sekulow denied the allegation.

After Cohen pleaded guilty to lying to Congress, Mueller’s office confirmed in a court filing that Trump’s onetime lawyer had provided them information about his contacts with people “connected to the White House” in 2017 and 2018, and about the “circumstances of preparing and circulating” his false statement. They told a judge that they believed the information he gave them was both “relevant and truthful.”

The tenor of the interaction Cohen described is broadly consistent with how Comey said Trump asked him to end the FBI’s investigation into Flynn in early 2017. At the time, federal agents were investigating whether Flynn had lied to them about conversations with the Russian ambassador in which they discussed lifting sanctions the Obama administration had imposed over Moscow’s election meddling. Comey testified that Trump met alone with him in the Oval Office and told him Flynn was a “good guy,” and “I hope you can let it go.”

“I took it as, this is what he wants me to do. I didn't obey that, but that's the way I took it,” Comey said.

Lies, and the circumstances in which they were told, have been a central part of Mueller’s investigation.

Flynn pleaded guilty in 2017 to lying to the FBI and promptly agreed to cooperate with the special counsel. Prosecutors have offered few details about the substance of his cooperation, but confirmed in a court filing last year that he had described to them how other officials on Trump’s transition team came to repeat the same false statements to the public.

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'A much larger problem' in New York

Of all the potentially damaging claims that Cohen leveled during his daylong congressional testimony, one of them made clear that he was not done unloading on the man whose secrets he once ferociously guarded.

"I am in constant contact with the Southern District of New York regarding ongoing investigations," Cohen told lawmakers.

Then, over the course of several hours, he offered tantalizing clues about what that cooperation involves.

He brought copies of checks, one of them signed by Trump, that represented secret reimbursements for the $130,000 in hush-money Cohen paid to silence porn star Stormy Daniels during the 2016 campaign about her alleged affair with Trump. The $35,000 payment from Trump was dated Aug. 1, 2017, nearly eight months after his inauguration as president.

Cohen displayed Trump's financial statements, dating from 2011 to 2013, which the former attorney said exposed his one-time boss as a "cheat."

"It was my experience that Mr. Trump inflated his total assets when it served his purposes...and deflated his assets to reduce his real estate taxes," Cohen said.

He went on to claim that Trump once rigged an auction of his portrait when he allegedly enlisted Cohen to arrange a straw buyer to purchase the artwork to ensure that it sold for the highest bid of the event. Later, Cohen said, Trump directed his charitable foundation to reimburse the straw bidder $60,000.

The dealings of Trump's foundation have been at the center of separate review by the New York State Attorney General's Office.

In yet another reference to an ongoing federal investigation, Cohen told lawmakers that his last communication with Trump or a direct representative of the president – about two months after FBI agents raided his home and office – also is being reviewed by Manhattan prosecutors. Again, he did not elaborate.

Giuliani said that Trump's legal team is "fully" aware of what prosecutors in both Washington and New York are pursuing.

"Cohen did everything he could to create innuendo," Giuliani said. "I think we have no liability."

He described the hush-money payment as a "personal" matter, not a "political" contribution, suggesting that any payment was intended to counter "harassment."

"They can chase that all they want," Giuliani said.

Where that chase ends is unclear. But observers said the potential jeopardy for those around Trump is unlikely to end along with Mueller's inquiry.

"Cohen was as credible as any cooperating witness ever is," said David Weinstein, a former federal prosecutor in Miami. "But anytime you can provide documents, that material speaks for itself."

If Cohen's testimony about his cooperation – especially in New York – is accurate, Weinstein said: "This is a potentially much bigger problem they (the Trump team) are facing."