Special counsel Robert Mueller’s investigation just drew what appears to be its most direct line to date between President Trump’s 2016 campaign and Russia.

That line is drawn in a new court filing related to the upcoming sentencing of London attorney Alex van der Zwaan. Van der Zwaan has pleaded guilty to lying about his contacts with deputy Trump campaign manager Rick Gates and a person not named in the document, Person A. Person A appears to be a former Ukraine-based aide to Gates and Paul Manafort named Konstantin Kilimnik.

Here’s the paragraph:

“Fourth, the lies and withholding of documents were material to the Special Counsel’s Office’s investigation. That Gates and Person A were directly communicating in September and October 2016 was pertinent to the investigation. Federal Bureau of Investigation Special Agents assisting the Special Counsel’s Office assess that Person A has ties to Russian intelligence service and had such ties in 2016. During his first interview with the Special Counsel’s Office, van der Zwaan admitted that he knew of that connection, stating that Gates told him Person A was a former Russian Intelligence Officer with GRU.”

That Person A has had ties to Russian intelligence is not terribly surprising. Kilimnik’s personal history has been examined extensively by the media, including The Washington Post. He has denied being involved in Russian intelligence, but he served in the Russian military and attended a Russian military foreign language university that is seen as a breeding ground for intelligence agents.

What’s particularly significant in the Mueller filing, though, are six words: “and had such ties in 2016.” Prosecutors have said previously that a longtime Manafort and Gates associate had ties to Russian intelligence, but they have never said those ties remained during the 2016 campaign. In December, they said this associate was “a longtime Russian colleague . . . who is currently based in Russia and assessed to have ties to a Russian intelligence service.” Why those six words were added in this filing when they didn’t appear in a previous filing is the $64,000 question.

The other new piece here is that they say Gates described Person A (again, apparently Kilimnik) as “a former Russian Intelligence Officer with GRU.” (GRU is Russia’s military intelligence organization.) So according to van der Zwaan, Gates talked openly about Person A’s ties to Russian intelligence. Kilimnik told The Post in June that he has “no relation to the Russian or any other intelligence service.” Mueller is now apparently directly disputing that using Gates’s own words.

Ever since his guilty plea last month, van der Zwaan’s relation to the case has been unclear. We know he is the son-in-law of a prominent Russian Ukrainian banker, but as with other figures in this case, we have no idea why he lied to investigators. Was it an honest mistake, or was he covering something up?

The new van der Zwaan filing doesn’t shed a whole bunch of new light on that, but it does suggest that Mueller views Kilimnik as a possible link between the Trump campaign and Russia, and believes Kilimnik hasn’t been forthcoming about his ties to Russian intelligence. We also know that Manafort had been in contact with Kilimnik during the 2016 campaign and met him at least twice.

Whether that’s pertinent to the broader collusion investigation is something we’ll have to wait to find out. But those six words seem at least a little conspicuous.