Obstruction of justice
By 
This NBC story isn’t getting nearly the attention it should. It appears to represent a rare instance of some real leaking coming out of the Mueller team, but it buries the lede by focusing on the breakdown of negotiations between Trump’s lawyers and Mueller about interviewing Trump. Here’s the more interesting part:
Three sources familiar with the investigation said the findings Mueller has collected on Trump’s attempts to obstruct justice include: His intent to fire former FBI Director James Comey; his role in the crafting of a misleading public statement on the nature of a June 2016 Trump Tower meeting between his son and Russians; Trump’s dangling of pardons before grand jury witnesses who might testify against him; and pressuring Attorney General Jeff Sessions not to recuse himself from the Russia investigation.
The pardons as bribes possible charge is particularly significant, since it’s exactly the kind of thing that would come from a freshly flipped target. And beyond that, the leaking itself indicates both that Mueller is getting close to sending his report to Rosenstein, and that people in Mueller’s orbit are concerned about making sure news of the state of play gets out before Trump fires Rosenstein and Mueller.