New York Attorney General Eric Schneiderman's reported involvement in the Justice Department's Russia probe could give new ammunition to critics of special counsel Robert Mueller, who is aggressively investigating former Trump campaign chairman Paul Manafort.

Schneiderman and Trump first crossed paths in 2010, when the former Democratic state senator solicited a donation from Manhattan's iconic real estate mogul during his bid for attorney general. After defeating his Republican opponent, Schneiderman announced that he would press forward with a case against Trump's now-defunct online college, frustrating the wealthy New York businessman who had contributed $12,500 to his campaign.

Two years into his tenure as attorney general, Schneiderman sued Trump for fraud, seeking millions of dollars in restitution for former students who claimed they were swindled by Trump University. Trump agreed to a $25 million settlement just days after he won the 2016 election, but not before his campaign spokesman had blasted Schneiderman as a "partisan hack who has turned a blind eye to the Clinton Foundation for years."

Trump himself called Schneiderman a "lightweight" during his 2014 re-election bid against Republican candidate and former New York environmental conservation commissioner John Cahill.

Tensions between Trump and Schneiderman are likely to flare up again now that the New York attorney general is said to be working closely with Mueller on his investigation into Manafort. Politico reported Wednesday that the two seasoned prosecutors have exchanged evidence and discussed their findings frequently over the past few weeks.

A spokesperson for Manafort declined to comment on the report and said they were unsure if the former Trump associate had been contacted by Schneiderman's office.

"I'm not aware but if I knew, I'd still say the same thing: We don't discuss our conversations with investigators," the spokesperson said.

Schneiderman is currently spearheading at least two probes into the Trump family's finances, one of which involves allegations that Trump's son, Eric, shifted funds from his personal foundation to the Trump Organization, which he and his brother took over when their father entered the Oval Office. He opened a separate investigation last September into whether the Donald J. Trump Foundation had ignored state laws governing nonprofits.

But people close to the White House said Schneiderman's history of political donations to Democratic political candidates, and his decision to position himself squarely against the president, could help Trump discredit Mueller's investigation if he is still in search of a way to do so.

Schneiderman made a maximum campaign contribution of $2,700 to defeated Democratic presidential nominee Hillary Clinton in 2015, and previously contributed $2,000 to John Kerry's presidential bid in 2004.

"By entering this fight, [Schneiderman] guarantees Trump supporters will put in unlimited fund to expose and publicize his corruption," longtime Trump adviser Roger Stone told the Washington Examiner, adding that he was "very happy" to see reports that Schneiderman has reportedly been working with Mueller and his team.

"I seriously doubt the Trump Justice Department will look favorably on his activities," Stone added.

A separate source close to Trump said "the Schneiderman stuff is almost exactly what [Trump] needs to expose the ridiculous conflicts of interest within this investigation." Though the source cautioned that going after Mueller "has already proven to be counterproductive."

There is one key area where Mueller cooperating with Schneiderman could be problematic for Trump: It could lead to state-level charges that would potentially be outside the scope of the president's federal pardon power. Some analysts viewed Trump's controversial pardon of former Maricopa County Sheriff Joe Arpaio as a possible precursor to future clemency for associates ensnared in the Russia probe.

Following an interview with Trump last month, the New York Times reported that Trump had asked his aides and legal team to dig up dirt on the dozen-plus attorneys that Mueller, who had previously expressed an interest in becoming FBI director, hired after he was appointed special counsel.

"He was up here, and he wanted the job," Trump had said of Mueller during the Times interview. He later described his reaction when Mueller was named special counsel: "I said, ‘What the hell is this all about?' Talk about conflicts. But he was interviewing for the job. There were many other conflicts that I haven't said, but I will at some point."

Mueller's probe into Russian collusion in the 2016 election has intensified in recent weeks, with Manafort emerging as the primary focus of investigators. The special counsel's team has been examining bank records and financial transactions Manafort was involved in and has reportedly subpoenaed his spokesman Jason Maloni and ex-attorney Melissa Laurenza.

However, several former business associates who worked with Manafort on lobbying activities told the Washington Examiner earlier this month they had not been contacted by federal investigators.

The White House did not return a request for comment on Schneiderman's alleged involvement in the Russia probe.