Mueller just stepped over Trump's red line

“I am not involved in Russia,” he said.

But Trump’s description of his dealings doesn’t allow for the fact that national security problems and other quandaries might arise for the president if Russia is involved in him — either through potentially compromising business transactions and relationships in the U.S., or because of funds that might have flowed into his wallet years ago.

Sater’s company, the Bayrock Group, operated out of Trump Tower, just two floors beneath the Trump Organization’s headquarters. A former partner of Sater at Bayrock claimed that the company was run as a money laundering operation. Bayrock also allegedly got some of its funding from Eastern Europe and from Iceland, and the company paid Trump to put his name on their projects.

Although Bayrock eventually went dormant, Sater never left the Trump team. He tried to engineer a diplomatic overture to Ukraine in early 2017, an effort he reportedly undertook with Cohen and which he tried to present to Trump’s former national security adviser, Michael Flynn. And, of course, there is the 2015 Moscow deal he pitched to Cohen that Mueller is now examining.