Washington (CNN) Lawyers working for former Trump campaign chairman Paul Manafort accidentally revealed on Tuesday the clearest public evidence of coordination between the campaign and Russians, adding new details to the murky mosaic of potential collusion in 2016 -- including sharing polling data with an alleged Russian operative.

The explosive new information was buried in a court filing from Manafort's lawyers, though the portions about his contacts with a shadowy Russian during the campaign were meant to be redacted.

But the document was fully searchable, even the blacked-out parts, revealing fresh details about the core of the ongoing investigation led by special counsel Robert Mueller.

Here's a breakdown of the latest disclosures and how they might fit into the existing puzzle.

Relationship with Kilimnik

Close watchers of the investigation have been intrigued by the still-developing role of Konstantin Kilimnik, a Russian political consultant who worked closely with Manafort in Ukraine. They helped Moscow-friendly politicians get elected and hold onto power for nearly a decade.

Manafort and Kilimnik stayed in touch after their Ukrainian clients were ousted in 2014. They met twice in the United States during the 2016 presidential campaign, according to their own public statements. News reports have detailed their phone calls and emails in 2016, including one exchange where Manafort tried to use Kilimnik to reach a prominent Russian oligarch.

But Tuesday's filing revealed they had a third meeting, this time in the Spanish capital of Madrid. One redacted portion quoted Mueller's team: "After being told that Mr. Kilimnik had traveled to Madrid on the same day that Mr. Manafort was in Madrid, Mr. Manafort 'acknowledged' that he and Mr. Kilimnik met while they were both in Madrid." A spokesman for Manafort sought to clarify the filing in a statement Tuesday night, saying that the third meeting happened in early 2017, after the election.

The growing list of Manafort-Kilimnik contacts could be relevant to the collusion question because, according to previous court filings from Mueller, the FBI has assessed that Kilimnik "has ties to a Russian intelligence service and had such ties in 2016."

Many of their contacts happened while the Russian government was aggressively meddling in the US election. Court filings said Kilimnik was affiliated with the GRU, the Russian military intelligence agency that was responsible for hacking Democratic targets and orchestrating the WikiLeaks releases.

CNN reported in February 2017 that Manafort was among a handful of senior Trump advisers who were in constant communication with suspected Russian operatives during the campaign. At the time, Manafort told CNN in a statement, "that is 100% not true, at least as far as me."

Sharing campaign polls

Beyond the fact that Manafort was in regular touch with Kilimnik, the unredacted court filings shed new light on the content of some of their conversations. For the first time, the public learned that Manafort shared "polling data" about the 2016 campaign with his Russian friend.

"Issues and communications related to Ukrainian political events simply were not at the forefront of Mr. Manafort's mind during the period at issue and it is not surprising at all that Mr. Manafort was unable to recall specific details prior to having his recollection refreshed," Manafort's lawyers wrote. "The same is true with regard to the Government's allegation that Mr. Manafort lied about sharing polling data with Mr. Kilimnik related to the 2016 presidential campaign."

There aren't any additional details -- all this tells us is that Mueller believes that Manafort fed polling data to Kilimnik, possibly even polls commissioned by the Trump campaign.

Polling data is a key part of any modern political operation -- presidential campaigns and outside groups like super PACs spend millions of dollars on polls. These numbers can drive decisions on messaging, where to campaign and advertising, both on television and in the digital space.

Trump's son-in-law Jared Kushner and 2020 campaign manager Brad Parscale ran Trump's data team in 2016. They've publicly touted about how they used data to target voters.

It's possible Manafort innocuously gave the polls to Kilimnik because he is a political junkie and wanted to dig into the crosstabs. But there's also a possibility that Kilimnik, with his active ties to Russian intelligence, funneled the information to Russian agents to influence the election.

The primary suspect would be the "troll farm" in St. Petersburg that essentially acted as a pro-Trump super PAC and pumped out political propaganda to millions of Americans on social media during the 2016 race. These messages can be targeted to specific demographics based on polling data. There aren't any publicly known ties between Kilimnik and the troll farm.

Ukraine peace plan

Tuesday's filing also unintentionally disclosed that Manafort and Kilimnik discussed a "Ukraine peace plan."

"After being shown documents, Mr. Manafort 'conceded' that he discussed or may have discussed a Ukraine peace plan with Mr. Kilimnik on more than one occasion," the filing said. The document was filed by Manafort's team, but this line appears to quote a past Mueller filing.

The filing revealed no details about what the Ukraine plan would entail. After Manafort's clients were ousted in 2014, Russian forced annexed Crimea and Kremlin-backed proxies invaded eastern Ukraine. Western nations condemned the moves and have applied economic sanctions against Moscow ever since. The diplomatic and military crisis is ongoing.

The news that Manafort was in talks with Kilimnik about a "Ukraine peace plan" is interesting, because it's not the first time the Ukraine conflict became an issue inside Trump's orbit.

During the 2016 Republican National Convention, Trump campaign officials intervened to change language in the GOP platform about the Ukraine conflict. Their actions blocked a provision that called on the US to arm the Ukrainian government to fight the Russian proxies.

At the time, Manafort denied that the Trump campaign was involved. He also said he was not personally involved in any effort to change the platform and learned of it from news reports.

The Ukraine issue came up again shortly before Trump's inauguration.

An informal "Ukraine peace plan" was hatched at a January 2017 meeting between Trump's longtime attorney and fixer Michael Cohen, former Trump business partner Felix Sater and Ukrainian lawmaker Andrii Artemenko. The proposal was seen by some as friendly to Moscow.

Cohen confirmed to CNN that the meeting took place but denied discussing Ukraine. In comments to other news organizations, Cohen acknowledged the so-called "peace plan" and said he delivered the proposal to the office of then-national security adviser Michael Flynn. The White House denied that anyone ever received any documents from Cohen about Ukraine.

It is not clear if this proposal was related in any way to the plan that Manafort discussed with Kilimnik. There aren't any publicly known ties between Artemenko and Kilimnik, though Kilimnik is an insider in Ukrainian political circles and has relationships with many lawmakers there. Artemenko has cooperated with Mueller and testified before the grand jury last summer.