Now that special counsel Robert Mueller has opened a federal investigation into Tony Podesta and his Washington lobbying firm, a probe that reportedly grew out of his investigation of ex-Trump campaign chairman Paul Manafort's finances, both Podesta and the firm could face consequences for work they completed on behalf of a pro-Russia Ukrainian think tank from 2012 to 2014.

The Podesta Group filed a retroactive Foreign Agents Registration Act disclosure in April acknowledging that its lobbying efforts on behalf of the European Centre for a Modern Ukraine could be interpreted as having principally benefitted that country's government. The firm has maintained it had no reason to believe its work justified FARA disclosure at the time, but Mueller will likely be probing whether that was indeed the case or whether they avoided filing with FARA to keep details of the ECMU away from scrutiny.

"Podesta Group CEO Kimberly Fritts said in a statement that the firm relied on assurances from the think tank, the European Centre for Modern Ukraine, that it was not controlled or financed by a foreign government or political party," Politico reported in April. "Based on that information, the firm disclosed its work to Congress rather than to the Justice Department."

"We believe the LDA registration was appropriate for our particular work on the Centre's behalf," Fritts said in her April statement. "However, we also understand after constructive consultation with FARA Unit staff that their position, which is based on all the information available to them, is that the overall representation is better classified as a FARA registration. Therefore, today the Podesta Group has reclassified its previous LDA registration for the Centre to a FARA registration."

That's fair enough.

But in the 14 months since the AP broke its initial story, a host of sources speaking to media have offered accounts that suggest the firm should have known to file a FARA registration at the time of its work for the ECMU.

In the AP's initial report, a former Podesta employee said that Rick Gates, who claims to have introduced the ECMU to the Podesta Group and Mercury, "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." As I noted on Monday, 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."

Following the Podesta Group's retroactive filing in April, CNN spoke to several 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.

"They were pretty open about their purpose being to give a positive perspective on the upcoming election," said a former State Department employee who met with the Podesta Group around the time of Ukraine's parliamentary elections in 2012.

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

Seven sources is not insignificant. Combined with the AP's current and former Podesta sources -- one of whom said Gates described the ECMU in 2012 as a source of money that could not be traced back to his benefactors in the Ukrainian government, and another of whom said they personally considered the work "obviously illegal" -- there's a possibility the firm deliberately filed a less-detailed LDA disclosure knowing a FARA registration would have been more appropriate.

Though it was years late and came only after media exposure, since the Podesta Group itself has retroactively filed the appropriate paperwork with FARA -- an admission its work for the ECMU met those standards -- it stands to reason Mueller is interested in finding out whether the firm knowingly skirted that requirement at the time of its initial filings.

Emily Jashinsky is a commentary writer for the Washington Examiner.