President Trump’s critics have long argued that he was corruptly trying to thwart the Russia investigation by dangling his broad pardon power. One of Trump’s many controversial pardons this week, in particular, raises that question anew.

Throughout the nearly two-year investigation into the Trump campaign’s ties to Russia, there was perhaps one person (aside from the president himself) whom investigators really wanted to talk to, and who ended up not cooperating and getting a lengthier jail sentence instead: former Trump campaign chairman Paul Manafort.

Now, Manafort is freed by the president from serving the rest of his 7½-year prison sentence. We don’t know whether there was an explicit deal between Trump and Manafort to reward the latter for his silence. But reports that Trump, through emissaries, floated the idea of a pardon to Manafort as he was talking to special counsel Robert S. Mueller III sound even more plausible now that it’s actually happened.

Manafort was one of the marquee names in a large batch of controversial pardons and commutations of sentences that the president announced this week.

Trump wasn’t necessarily quiet about his desire for Manafort to stay quiet. During the Mueller investigation, Trump publicly praised Manafort for refusing “to break.” Manafort originally fought criminal charges, and then, facing 10 years in prison, pleaded guilty in hopes of a lesser sentence for cooperating with Mueller. But the plea deal almost immediately collapsed as Mueller accused Manafort of lying to him and his team — about his contacts with a potential Russian agent, no less.

Trump has also pardoned or commuted the sentences of four other people caught up in the Russia investigation, not even hiding the fact in statements that he wants to try to undo the work of an investigation that dominated much of his presidency.

But Manafort’s pardon rises above the rest for its ability to hide any Russia ties with the Trump campaign from investigators. Some of the others Trump helped with legal troubles — former national security adviser Michael T. Flynn and former campaign aide George Papadopoulos — ended up cooperating in some form with investigators.

The nature of the highly secretive special counsel investigation is that we won’t know exactly what they shared with investigators. But they clearly shared something of value, given that Mueller didn’t throw the book at them like he did with Manafort. They were convicted or went to jail on lesser sentences for their cooperation. (Flynn got his conviction overturned with the help of former Trump attorney general William P. Barr.)

(Trump ally and operative Roger Stone, like Manafort, notably did not cooperate with Mueller. Trump pardoned him this week too, after commuting his sentence for, in part, lying to Congress about conversations he had with Trump campaign officials.)

We don’t know and may never know exactly what Manafort knew. But we know that Mueller really wanted to talk to him. Manafort had perhaps the most connections to Russia of anyone. He had worked for pro-Russian political forces in Ukraine before joining the Trump campaign. His brief tenure as head of Trump’s campaign overlapped with concerns about Russia’s interference in the 2016 election. He was in the Trump Tower meeting with a Russian lawyer and Donald Trump Jr., taking notes on his phone. He has high-level connections to Russia in his own right. Someone Manafort worked closely with, Konstantin Kilimnik, was described by Mueller as having “ties to Russian intelligence.” A Senate Republican report went further and called Kilimnik a “Russian intelligence officer,” and said he was the “single most direct tie” between the Trump campaign and Russian intelligence, so much so that Kilimnik was “at the center of the Committee’s investigation.”

Manafort shared Trump campaign polling data with Kilimnik. As The Fix’s Aaron Blake pointed out, Manafort’s plea deal fell apart when investigators accused him of lying about his contacts with Kilimnik.

Why would he lie specifically about that, if there wasn’t the potential for a pardon? The Senate Republican-led investigation into this raises that question in its report:

Manafort’s obfuscation of the truth surrounding Kilimnik was particularly damaging to the Committee’s investigation because it effectively foreclosed direct insight into a series of interactions and communications which represent the single most direct tie between senior Trump Campaign officials and the Russian intelligence services. Manafort’s true motive in deciding to face more severe criminal penalties rather than provide complete answers about his interactions with Kilimnik is unknown, but the result is that many interactions between Manafort and Kilimnik remain hidden.

As Blake wrote: “It raises the idea that Manafort’s lies on this count are inexplicable because he effectively resigned himself to more jail time. Raising that unknown motive isn’t necessary, but it would seem to have been included for a reason.”

Especially when you consider that according to the FBI, in 2018, as Manafort was fighting charges, he told his deputy, Rick Gates, that they would “get through it” and “we’ll be taken care of,” as BuzzFeed’s Jason Leopold pointed out.

In his confirmation hearing to be attorney general, Barr testified that he thought that it would be corrupt, even criminal, for a president to issue a pardon in exchange for someone not to give incriminating evidence. “That would be a crime,” he said unequivocally.

We don’t know whether Manafort had incriminating evidence. We may never know, because Mueller didn’t get to talk to him. Another crucial point is whether there was an explicit understanding or Manafort was just inferring that he would be “taken care of.” According to that 2018 FBI document, care was taken between parties not to use the word “pardon.” But the FBI also suggests that Manafort was in touch with Trump’s legal team, and he and Gates did talk about pardons.

As he’s since written, Mueller wasn’t doing this to tear at Trump’s presidency. He had a job to do to understand how Russians tried to infiltrate and shape an American presidential election, and whether anyone in the United States helped with that.

“Russian efforts to interfere in our political system, and the essential question of whether those efforts involved the Trump campaign, required investigation,” Mueller wrote in a rare op-ed for The Washington Post after Trump first waived Stone’s jail time this summer.

Mueller never got to probe all of this as much as he wanted. Instead, arguably the central figure in all this stayed quiet. And he just got rewarded for that with a get-out-of-jail-free card from the president of the United States.

Aaron Blake contributed to this report.