While working unpaid for Donald Trump’s presidential campaign, Paul Manafort mused about how he could use his new prominence to get financially “whole,” and offered to give private political briefings to a Russian billionaire who had recently sued him.

That’s according to Manafort’s own emails with a business associate, which are currently being examined by investigators and are described in a new report from the Washington Post’s Tom Hamburger, Rosalind Helderman, Carol Leonnig, Adam Entous.

Furthermore, at least one email appears to use some sort of code, with Manafort’s associate apparently referring to the Russian billionaire — Oleg Deripaska — as the person “who gave you the biggest black caviar jar several years ago,” saying they should discuss his situation more in person.

Manafort’s spokesperson says the briefing never ended up happening. But at a time when Manafort is under a great deal of legal scrutiny in the investigation into potential collusion with Russia, the revelations raise further questions about just how he was using his position.

It was reported earlier this week that Manafort was wiretapped by the federal government at some points in 2016 and 2017, and that special counsel Robert Mueller’s team has told him to expect an indictment.

The emails in question

There are three key emails described in the Post story. They are:

1) An April email sent in the opening days of Manafort’s work for Trump in which Manafort ‘referred to his positive press and growing reputation and asked, “How do we use to get whole?”’

2) A July 7, 2016, email in which Manafort told his Ukrainian business associate Konstantin Kilimnik to let Deripaska know that he could give him private briefings on the presidential campaign. “If he needs private briefings we can accommodate,” Manafort wrote, according to the Post.

3) A July 29, 2016 email in which Kilimnik appeared to speak in code to Manafort about a meeting he’d just had with Deripaska. Kilimnik said he’d met with the person “who gave you the biggest black caviar jar several years ago.” He also wrote that it would take time to explain this “long caviar story.” He and Manafort then set up a meeting in New York, which took place a few days later.

Manafort was working on the Trump campaign during all of these email exchanges (and indeed, he used his official campaign email account for them, according to Politico’s Josh Dawsey). He was fired from the campaign in mid-August.

What’s going on here?

It’s long seemed strange that when Paul Manafort worked on Donald Trump’s presidential campaign, he agreed to do so unpaid — despite being in millions of dollars’ worth of debt.

The backstory here relates to Manafort’s finances and long business relationship with Deripaska, the billionaire in question.

Deripaska is a Russian oligarch and aluminum magnate who Manafort has known since at least 2004 and done a good deal of consulting work for over the years. The Wall Street Journal’s Brett Forrest recently chronicled what’s known of their relationship, and according to his account, Deripaska helped set Manafort up for what turned out to be years of lucrative work for pro-Russian political parties in Ukraine.

Crucially, though, the two had a falling out — in 2014, Deripaska sued Manafort in a Cayman Islands court and claimed he had cheated him of millions of dollars.

So by the time Manafort was on the Trump campaign, he seems to have been trying to figure out how to repair his relationship with Deripaska. That’s how the offer of “private briefings” came in.

The question is what happened next. The coded language Kilimnik apparently used to refer to Deripaska — he referred the person “who gave you the biggest black caviar jar several years ago” — suggests there is a “story” there that Manafort and Kilimnik later discussed in person.

And special counsel Mueller’s investigators are likely very interested in just what that story is, as they try to put Manafort in more and more legal jeopardy in an apparent attempt to get him to turn on his onetime allies.