Rudy Giuliani, the president’s lawyer and lead spokesman in legal matters, promptly and furiously denied that Trump was aware of the meeting, calling Cohen a liar. At the moment, there’s no public evidence to adjudicate the dispute. There is, however, a pattern that is uncomfortable for the president. On two separate but related matters that converge with this new allegation, the president and his team have been caught repeatedly lying. First, the White House in July 2017 offered false stories about the Trump Tower meeting, only to have to promptly admit they were incorrect. Second, the Trump team repeatedly insisted that the president was unaware of payments to Karen McDougal and Stormy Daniels, two women who allege they had affairs with him. But a tape released by Cohen shows Trump was aware of the plan to buy McDougal’s story and suffocate it, while Trump acknowledged reimbursing Cohen after his payment to Daniels.

If if is true that Trump was aware of the meeting, and that Cohen is willing to testify, it would be a dramatic development. Trump and his son have both denied that the father was aware of the meeting at the time. The White House said in July 2017, when the meeting was first reported, that the president had only recently learned about it. Trump Jr. told the Senate Judiciary Committee the same thing in September 2017. Although he was not under oath, lying during that testimony would still be a criminal offense.

“He wasn’t aware of it,” Trump Jr. said of his father. “And, frankly, by the time anyone was aware of it, which was summer of this year, as I stated earlier, I wouldn’t have wanted to get him involved in it because it had nothing to do with him.”

Some other observers have also speculated Trump must have known about the meeting—most prominently Steve Bannon, who joined the Trump campaign later in the summer of 2016 and then served as White House chief strategist. Speaking to the reporter Michael Wolff, Bannon said that there was “zero” chance the candidate didn’t know about the meeting. But no one has come forward with specific knowledge that the father knew of the meeting.

Testimony that Trump Sr. was aware of the meeting would also further illuminate allegations of collusion between the Trump campaign and Russia. There is extensive evidence of contacts between Trump aides and Russians, much of it surreptitious. As I wrote in July 2017, the Trump Tower meeting doesn’t prove there was collusion per se, but the circumstances show a willingness by top campaign officials to collude with Russia. Before the meeting, Trump Jr. received emails indicating that the Russian with whom he was meeting had dirt to offer, and also stating that the Kremlin backed his father’s candidacy. If Trump Sr. was also aware of the meeting, it would appear to extend the willingness to collude to the candidate himself.