Michael T. Flynn speaks at the White House. (Carlos Barria/Reuters)

Special counsel Robert S. Mueller III and his team are no strangers to the practice of prosecutorial hardball. That skill may be coming into play once again if, as news reports indicate, the special counsel is turning his attention to former national security adviser Michael T. Flynn and Flynn’s son Michael G. Flynn, who worked with his father’s lobbying firm and was also involved in the Trump transition. The elder Flynn has long been thought to be in Mueller’s sights, and CNN reported Wednesday that Flynn and his wife are worried about their son’s legal exposure as well.

If in fact prosecutors have built cases against both men, they now have a huge, juicy carrot to dangle in front of the elder Flynn: Plead guilty and testify against others, and we’ll go easy on your son. Given the former national security adviser’s prior positions with the Trump campaign and administration, that prospect has to make other potential targets of Mueller’s inquiry extremely uneasy.

Members of Mueller’s team are very familiar with — and have not been shy about employing — the tactic of persuading a witness to cooperate in exchange for leniency toward a family member. His chief deputy is Andrew Weissmann, a career prosecutor with a reputation for aggressiveness. More than a decade ago, Weissmann served on and ultimately headed the Enron task force, the team of prosecutors charged with investigating the financial collapse of the huge energy corporation. Weissmann and the other Enron prosecutors wanted the cooperation of Andrew Fastow, Enron’s former chief financial officer, whom they had indicted on dozens of federal charges. When prosecutors later added additional charges against Fastow, they also indicted a new defendant: Lea Fastow, Andrew’s wife, who had also worked at Enron. With the felony charges pending against Lea Fastow, the couple faced the prospect of spending years in prison while their two young sons were raised by others.

President Trump's troubles have only just begun with Special Counsel Robert Mueller's charges against former Trump campaign manager Paul Manafort, his associate Rick Gates and former foreign policy adviser George Papadopoulos, says Washington Post editorial writer Quinta Jurecic. (Adriana Usero,Kate Woodsome/The Washington Post)

Andrew Fastow ultimately agreed to plead guilty to two conspiracy charges, serve 10 years in prison and cooperate in the investigation. Prosecutors allowed Lea Fastow to plead guilty to a single misdemeanor tax charge. She also was allowed to complete her one-year sentence before her husband was sent to prison, thus allowing the couple to avoid overlapping jail time and care for their children.

Both Fastow plea deals were announced on Jan. 14, 2004, by none other than then-Deputy Attorney General James B. Comey and then-FBI Director Mueller. The plea agreements were linked, so if Andrew Fastow didn’t follow through on pleading guilty and cooperating, Lea Fastow’s deal could be revoked. Andrew Fastow went on to be the government’s star witness at the trial of former Enron top executives Kenneth Lay and Jeffrey Skilling, whose convictions became the biggest feathers in the task force’s hat.

If anyone had any lingering doubts, the Fastow story is further evidence that these prosecutors don’t play around. Hardball doesn’t get much harder than showing a guy you’re willing to jail his wife and effectively orphan his kids if he doesn’t cooperate. Even the most hardened prosecutor might feel a slight twinge in the gut at the prospect of using a defendant’s young children as leverage against him. But there is little doubt that Mueller’s team will deploy whatever weapons it has to persuade the inquiry’s targets to play ball.

Of course, the younger Flynn is an adult, not a child. Almost any prosecutor would likely agree that using legitimate charges against him as leverage against his father is fair game. And almost any parent would likely agree that the chance to protect your offspring — even if they are adults — provides an enormous incentive to cooperate. If given that option, the elder Flynn may find it difficult to resist.

As Mueller’s investigation proceeds, this tactic could face a unique twist. If prosecutors continue to close in on President Trump’s inner circle, his own family members, including his son Donald Trump Jr. and son-in-law Jared Kushner, could be implicated. Potential charges against Trump’s family would give prosecutors tremendous leverage over the president himself. But in this particular game of hardball, the target would have some leverage of his own: the pardon power and the ability to fire the prosecutor.

When it comes to protecting his family, Trump has options that Andrew Fastow never had. If the time comes, whether and how he chooses to exercise those options could have profound implications, not just for this investigation but also for the rule of law and the entire country.