Editor's Note: (Caroline Polisi is a federal and white collar criminal defense attorney at Pierce Bainbridge in New York City and an adjunct Lecturer in Law at Columbia Law School. She frequently appears on CNN as a legal analyst. Follow her on Twitter: @CarolinePolisi. The views expressed in this commentary are her own. Read more opinion on CNN.)

(CNN) The arrest on Thursday of two associates of Rudy Giuliani on campaign finance charges has people asking the obvious question: what does this mean for the Trump impeachment investigation?

The Southern District of New York's 21-page indictment offers a few clues. The defendants, Lev Parnas and Igor Fruman, along with two others, are accused of a straw-donor scheme to make money and advance the political interests of at least one Ukrainian government official. Sound familiar?

Most gallingly, the indictment alleges that Parnas and Fruman sought help from a sitting congressman to remove or recall the US ambassador to Ukraine, Marie Yovanovitch. While neither the indictment nor the US attorney who announced it, Geoffrey Berman, mentioned President Trump or Giuliani, his personal lawyer, it's hard to resist putting two and two together.

Yovanovitch was reportedly removed after complaints from Giuliani and others that she was thwarting his efforts to coax the Ukrainian government to investigate former Vice President Joe Biden and his son Hunter, according to the Wall Street Journal.

We are also learning more details daily about the now-infamous July phone call between Trump and Ukrainian President Volodymyr Zelensky, in which Trump asked for a "favor" in the form of an investigation into his political rival, now the basis for a whistleblower complaint.

Given these various and related threads, what's the likelihood that Giuliani is not involved?

What should worry Giuliani most is that Berman emphasized that the investigation is "ongoing." Indeed, the indictment indicates that the investigation has been fulsome and aggressive to this point, (and most likely included the wiretapping of Parnas' and Fruman's devices).

As we know from the prosecution of Michael Cohen for campaign finance law violations, prosecutors in the Southern District will give coveted "cooperator" status only to defendants who are willing to discuss every instance of criminal wrongdoing in which they were involved or know about. Cooperators cannot pick and choose what they reveal -- it's all or nothing. That means that if Parnas or Fruman are allowed to exchange information for leniency at sentencing, they would have to spill what they may have on Giuliani.

John Dowd, Trump's former personal attorney, who is representing Parnas and Fruman, had no comment on the indictment.

Jay Sekulow, another Trump lawyer, has already declared that neither the President nor his campaign had anything to do with the two men indicted. And when Giuliani was asked by a reporter about the prospect of the FBI flipping Parnas and Fruman for damaging information on him, he replied, in typical Giuliani fashion, "Good luck."

Good luck, indeed. We know that both Parnas and Fruman helped Giuliani to try to dig up dirt on the Bidens. But the question of whether that relationship overlaps with criminal conduct is a mystery, for now.