Special counsel Mueller has told a court at least one member of Trump's campaign was knowingly working with a former Russian spy.

Late on Tuesday evening, a new bombshell report revealed special counsel Robert Mueller has alleged in a court filing that former Trump campaign aide Rick Gates knew that he and chairman Paul Manafort “were working with a former Russian intelligence officer during the 2016 election.”

The allegation, which appears in the sentencing document against attorney Alex van der Zwaan for lying to Russia investigators, also reveals the officer still had ties to Kremlin intelligence during the campaign, whether or not Gates knew that.

This blows the lid off one of Trump’s main defenses against the allegations: that Mueller’s indictments against campaign officials, and subsequent guilty pleas, are not about Russia.

Trump initially tried to deny Russia was behind foreign election interference at all despite receiving briefings during the election saying so. And as the Mueller indictments stacked up, he and his defenders tried to claim the charges Mueller has brought have “nothing to do” with Trump, or with Russian collusion.

Until now, this defense, though implausible, was not entirely disproven. Manafort and Gates were indicted for money laundering and fraud, not conspiring with Russia per se. George Papadopoulos and Michael Flynn, like van der Zwaan, both pled guilty to lying to investigators, not any criminal activity involving Russia itself. And while Mueller did indict 13 Russians for election interference, he did not directly allege in the indictment that they had inside help.

But Mueller’s new allegation is impossible to brush aside. He believes at least one member of Trump’s team knowingly worked with someone linked to the Kremlin, during the 2016 election campaign. So Trump can no longer say the investigation has nothing to do with Russia collusion.

As Mueller uncovers the truth little by little, Trump’s team has had to move the goalposts again and again. There is now little left that they can deny happened — and there are few publicly known facts left that they can defend.