On Friday prosecutors filed three highly anticipated documents related to the investigation by special counsel Robert S. Mueller III. Allegations about hush-money payments and possible campaign finance violations by the president grabbed a lot of attention. But the key takeaway is this: A robust investigation into President Trump’s ties to Russia continues — and the administration’s legal peril based on those ties continues to grow.

Least revealing was the special counsel’s filing in Paul Manafort’s case, explaining why prosecutors believe Trump’s former campaign chairman repeatedly lied to them after agreeing to cooperate. Much of the information was under seal, and the portions we could see contained no bombshells. Many of Manafort’s lies apparently concerned his contacts with suspected Russian intelligence officer Konstantin Kilimnik, and most of that information was redacted, which suggests it may relate to the broader inquiry into Russian contacts with the campaign and not merely to Manafort’s personal financial dealings. But we will have to wait and see.

The two more interesting filings related to the sentencing of Michael Cohen, Trump’s former attorney. Cohen pleaded guilty to financial and campaign finance crimes in a case brought by prosecutors in the Southern District of New York, and then pleaded guilty to lying to Congress in a separate case brought by Mueller. Cohen’s lies to Congress related to a project to develop a Trump-branded tower in Moscow. Cohen told Congress the project had been abandoned by January 2016, when in fact negotiations continued through June, while Trump was wrapping up the Republican nomination.

Each prosecutor’s office filed its own sentencing memo related to Cohen. Mueller’s memo said Cohen had provided helpful and credible information related to his own Russian contacts during the campaign, information regarding “certain discrete Russia-related matters core to [the special counsel’s] investigation,” and his contacts with people connected to the White House in 2017 and 2018. We don’t know what “discrete Russia-related matters” are, but that no-doubt deliberately vague phrase covers a wide range of possibilities involving the campaign or Trump’s business interests. It’s clear that a good portion of Cohen’s extensive cooperation related to the heart of Mueller’s probe: possible criminal violations related to contacts with Russian interests.

Also intriguing was the report that Cohen told Mueller about the “circumstances of preparing and circulating his response to the congressional inquiries.” This raises the possibility that Cohen did not act alone when lying to Congress about the Moscow tower project; his answers may have been vetted by others. Anyone else involved would potentially be implicated in a coverup conspiracy.

Prosecutors in the Southern District of New York, who are not part of Mueller’s team, were much harder on Cohen in their sentencing memo. They said Cohen refused to fully cooperate with their office or discuss the full range of his own misconduct. They agreed he deserved some credit for cooperating with the special counsel but still called for a sentence of several years in prison.

Part of Cohen’s guilty plea in the Southern District case was to making illegal campaign contributions by paying off women threatening to expose their alleged affairs with candidate Trump. In their filing, prosecutors repeated what Cohen had already said in court, that when he paid the hush money he “acted in coordination with and at the direction of Individual-1” — Trump. This single phrase in a 38-page memo set off a barrage of claims that prosecutors had implicated the president himself in a felony.

The reality is more complicated. Although for most crimes ignorance of the law is no excuse, criminal campaign finance violations must be “willful,” which means the government must prove the defendant knew he was breaking the law. If Trump directed Cohen to pay women off but was not aware of the campaign finance implications, he may not be criminally liable, although conspiracy to defraud the United States, which does not require willfulness, might also be in play.

But the raging debate about the hush-money payments is something of a sideshow. Although serious, campaign finance violations often are not criminal and certainly are not the key issue here. The key is Russia, and Cohen has joined the ranks of other cooperators providing Mueller with extensive information on those issues. We now know Trump was secretly negotiating a deal with Russia worth hundreds of millions of dollars while running for president and while Russia was actively working to help him get elected. There is mounting evidence of substantial connections among Russia, the Trump campaign, and Trump’s business interests, and of a possible criminal conspiracy to conceal those connections.

Each new court filing reveals a few more pieces of the puzzle Mueller has been assembling. The picture that’s emerging suggests that Trump — and the country — have far bigger things to be concerned about than the intricacies of campaign finance law.

Read more:

Harry Litman: What to watch for in Friday’s Mueller filings

Paul Waldman: The latest filings show that nobody can save Trump now

Brian Klaas: The Mueller investigation has been a series of drips. It’s about to turn into a flood.

The Post’s View: William Barr believes in Justice Department independence. He might have to fight for it

Jennifer Rubin: What the Senate must ask William Barr