Roger Stone has been a close friend of, lobbyist for, and adviser to Donald Trump for decades. It’s been suggested he’s one of the few people Trump trusts completely.

So it should come as no surprise that Stone was one of the key figures in Trump’s 2016 campaign for president. And he may now wind up being the person most essential to proving that Trump was involved in a conspiracy with Russia to steal the last election.

This week, Jonathan Chait of New York magazine laid out exactly what damaging information Roger Stone has and how that may impact Trump in the months ahead, especially if Democrats retake control of just one house of Congress:

“Stone communicated regularly and directly with Trump during the campaign. The odds that Stone, a notorious braggart seeking to curry favor with Trump — notorious also for being unhindered by ethical scruples — would fail to share his knowledge of what the hackers had up their sleeves are extremely remote.”

Stone has famously said there’s no way in hell he would ever cooperate with Special Counsel Robert Mueller — “I will never roll on Donald Trump!” — but that’s what former campaign chairman Paul Manafort also said before he accepted a plea deal and began spilling his guts to the special counsel’s team of investigators.

And here’s the catch: Even if Stone remains adamant and refuses to say a word to Mueller, it may not matter in the least, as Chait explains:

“If … Stone shared his inside knowledge about WikiLeaks with other Trump campaign officials, then it might not matter if he keeps his mouth shut. Those officials, some of whom have rolled on Trump already, could tell Mueller what Stone knew, and even what he told Trump. One likely candidate to have heard some word from Stone is Paul Manafort, Stone’s former business partner and a current Mueller witness. That testimony could very easily establish Trump’s role as an accessory after the fact to Russian hacking.”

Also, if Stone does stick to his guns and refuse to tell what he knows, he could be facing 20 or more years in prison for conspiracy to defraud the United States as part of the election scandal. Stone is 66 years old and might be in his late eighties or early nineties before he breathes free air again if convicted. That fact alone is often enough to convince even the most recalcitrant witnesses to spill their guts.

Stone is the key to the Russia probe, and he may not have to say a word to completely destroy Donald Trump.