Democratic lobbyist Tony Podesta and the Podesta Group, his powerful Washington firm, are now caught up in a federal criminal investigation by special counsel Robert Mueller. They may have violated the Foreign Agents Registration Act by failing to properly disclose work completed on behalf of a pro-Vladimir Putin Ukrainian think tank to the Justice Department.

By filing a retroactive FARA disclosure this April, the firm admitted those lobbying efforts, which took place between 2012 and 2014 on behalf of the European Centre for a Modern Ukraine, may have principally benefitted that country's government. The investigation of Podesta grew out of Special Counsel Robert Mueller's probe of Paul Manafort, according to NBC News, which broke the story on Monday. Manafort and associate Rick Gates introduced the Podesta Group and another lobbying firm, Mercury LLC, to the ECMU, per Gates' account.

The Podesta Group's involvement with the ECMU was first reported in an Associated Press story on Manafort, then-Trump campaign chairman, in August of 2016. The firm maintained it did not have reason to believe its work on behalf of the ECMU warranted a FARA disclosure in 2012, but nevertheless filed a belated disclosure this spring after exposure in the press.

Speaking to news outlets over the past 14 months, several sources have cast doubt on the Podesta Group's insistence that it was unaware the nature of its work warranted disclosure to the DOJ.

In the AP's initial report, a former Podesta employee "said Gates described the nonprofit's role in an April 2012 meeting as supplying a source of money that could not be traced to the Ukrainian politicians who were paying him and Manafort." Three other current and former Podesta employees told the AP disagreements broke out between staff over its decision to take on the work, which one of those sources considered to be "obviously illegal."

After the Podesta Group filed retroactively in April, CNN spoke to people who had been lobbied by the firm over the course of its work for the ECMU. Dan Harsha, who was lobbied in 2013 while serving as communications director for Democrats on the House Foreign Affairs Committee, told CNN "It seemed pretty clear [the center] was just a front" for former Ukrainian President Viktor Yanukovych. A former State Department employee who met with the Podesta group around the time of Ukraine's " bellwether" parliamentary elections in 2012 said, "They were pretty open about their purpose being to give a positive perspective on the upcoming election."

CNN reported that seven sources said the Podesta Group "left a clear impression that they were representing Ukraine's government" as lobbyists held meetings around Washington.

In that case, the firm's decision not to file with the DOJ until after its work for the ECMU leaked into the press, and then after the 2016 presidential election, looks highly suspect. As the AP put it, "Lobbyists in general prefer not to register under the foreign agents law because its requirements are so much more demanding, making their activities more open to public scrutiny."

In addition to his brother John Podesta's position at the helm of the campaign, it's well worth noting, as most outlets have failed to do, that Tony Podesta was a prominent fundraiser for Hillary Clinton's 2016 bid for the White House.

The Podesta Group's efforts on behalf of the ECMU, per its belated disclosures, show the firm made contact with Clinton's State Department, the National Security Council, and the office of former Vice President Joe Biden over the course of its lobbying campaign to soften the Obama administration's position towards Ukraine's then-pro-Russian government.

In his investigation, Mueller will likely probe what Podesta and his firm knew about the ECMU's connections to the Ukrainian government when deciding how to disclose its lobbying efforts on their behalf.

Emily Jashinsky is a commentary writer for the Washington Examiner.