The Trump family has had longstanding real estate and licensing dealings with questionable business associates, some of them Russian and some of them not, as I and reporters like the late Wayne Barrett have written about for years. …
While Trump allies have recently targeted [Robert S.] Mueller’s probe as ill-founded, tainted with prosecutorial bias, and the work of a conspiracy orchestrated with Democratic partisans and the “deep state,” the reality is that Mueller — a well-regarded, veteran prosecutor — has been running a by-the-books investigation.
It’s an investigation that is likely to continue examining matters beyond political collusion — which Mueller’s original mandate allows for — and will continue to involve explorations of financial dealings by the Trump family and members of the Trump campaign (particularly those involving Russia).

O’Brien and other observers have speculated that Trump’s finances hang like the sword of Damocles over his presidency. It’s for this reason, the theory goes, that Jared Kushner repeatedly omitted information about his finances and about meetings with foreigners from his security clearance application, signed under penalty of perjury. It’s why Kushner’s meeting with a Russian banker during the transition was not originally disclosed. It’s why, as Stephen K. Bannon pointed out, Mueller has stocked his team with plenty of money-laundering and other financial crimes gurus.

Opinion | If President Trump fires the bane of his legal troubles, he could spark a legal and constitutional crisis. (Adriana Usero/The Washington Post)

It’s why Mueller has gotten records from Deutsche Bank pursuant to a subpoena. And it is why, as CNN reported, the Trump organization has had to cough up its own share of documents. CNN reported that the documents cover “a range of events, conversations and meetings from President Donald Trump’s real estate business to investigators probing Russian election meddling, according to three people familiar with the matter. The bulk of the information is focused on the period between June 2015, when Trump announced his candidacy, and his January 2017 inauguration.”

The importance of Trump’s finances would explain his dogged refusal to reveal his taxes and his outburst early in the investigation. (Trump can never contain himself, even at the price of self-incrimination.) Trump said that investigation of his finances would be a “violation” — a violation of what, is not clear. Asked whether that would be a “redline” he said, “I would say yeah. I would say yes.” (It’s noteworthy that with all the investigation into Trump’s finances, Trump hasn’t yet tried to fire Mueller. Perhaps his team has convinced him that would prompt serious talk of impeachment.)

And if Trump believed his finances were a source of vulnerability — or the election was an opportunity to do business in Russia — he might have been especially solicitous of Russian President Vladimir Putin during the campaign.

Finally, it may have been concern over his finances that prompted him to lash out to fire former FBI director James B. Comey.

At this stage, we simply don’t know whether Trump’s finances are legally problematic or politically embarrassing (e.g. he did deals with Russia when he had said he hadn’t). We don’t yet have any evidence that either he or his son-in-law did anything illegal. However, Mueller sure thinks there may be something there. We’ll find out by the time Mueller is done whether Bannon’s hunch is right or just more of his blather.