Special counsel Robert Mueller is reportedly focusing on possible financial crimes, including money laundering, by former Trump campaign chairman Paul Manafort, as part of an effort to squeeze Trump's inner circle on Russian collusion.

Special counsel Robert Mueller is reportedly looking toward possible money laundering or tax evasion by Paul Manafort, Donald Trump’s former campaign chairman, in order to potentially use those offenses to build a case for collusion with Russia.

McClatchy reports that two sources familiar with the ongoing inquiry say Mueller is trying to confirm that Manafort earned between $80 to $100 million from Ukranian and Russian clients over the last decade. Investigators are reportedly looking through Manafort’s complex web of offshore banks and business accounts to see if he hid that money while trying to avoid taxes.

Such charges against Manafort could prove crucial to the collusion investigation. As former Justice Department prosecutor Barak Cohen told McClatchy, “Based on my experience with prosecutors, it would be typical that they’re getting financial information to pressure Manafort to cooperate in a bigger case.”

McClatchy also notes that, “Given his pro-Kremlin connections and his closeness to the campaign, Manafort was uniquely positioned to play a role in any collusion between the campaign and operatives working on behalf of the Russian government to help elect Trump.”

Manafort was one of several key figures — including Donald Trump Jr. and Trump’s son-in-law, Jared Kushner — who met with Russian operatives at the height of the campaign, seeking damaging information on Hillary Clinton. And his home was recently the target of a pre-dawn FBI raid seeking documents related to his European financial pipeline.

After the raid, Manafort hired lawyer Kevin Downing, of the firm Miller and Chevalier, who specializes in defending clients in financial crimes cases.

Trump has repeatedly tried to derail the investigation, as it continues to unearth more sordid information.

He fired then-FBI Director James Comey while pressuring Comey to make public statements distancing Trump from the Russia investigation.

He complained when Attorney General Jeff Sessions — who met with the Russian ambassador while serving on the Trump campaign — recused himself from the investigation, telling the New York Times, “I think is very unfair to the president. How do you take a job and then recuse yourself?”

And it was recently exposed that Trump argued with Senate Majority Leader Mitch McConnell after he asked the top-ranking senator to “protect him” from the Russia probe.

To save his own hide, Trump is obstructing justice even as the multiple investigations show he and his top campaign lieutenants were lying when they said they hadn’t made contact with Russia.

But his behavior doesn’t seem to be scaring of Mueller and other investigators, who are now focusing on Trump’s inner circle as they get closer and closer to the truth.