Based on his words and actions during the course of the 2016 election, it was fairly clear all along that Donald Trump had some sort of agreement in place with the government of Russia when it came to several key foreign policy issues. It’s since come to light that the Trump campaign and Russia were plotting to alter the outcome of the election as well. Now it turns out Robert Mueller has uncovered evidence that Trump and Russia had a formal document in place regarding their election partnership.

Republican political strategist Mike Murphy appeared on the Lawrence O’Donnell show on MSNBC on Monday night. He said that a friend of a friend was recently hauled in by Robert Mueller to answer questions about a “memorandum of understanding” that Trump had with Russia during the election. According to Murphy, Mueller already has the document in question (link). Murphy has been a respected political insider for decades, and there is every reason to believe that his claims here are accurate.

In legal terms, a memorandum of understanding is essentially a non-binding contract. But the mere existence of such a document between Donald Trump and Russia, which spelled out what roles each side would play in their partnership in the 2016 election, sounds an awful lot like “smoking gun” territory when it comes to demonstrating that Trump was formally working for the Kremlin as a presidential candidate.

Robert Mueller has already brought criminal charges against at least nineteen people in Donald Trump’s Russia scandal, including at least four of Trump’s key advisers. Even as Mueller continues to cut plea deals and move his way up the ladder, the news about the memorandum of understanding is reminder that he’s made far more progress behind the scenes than what he’s publicly revealed to date.