The contents of the notes and the role played by Mr Cheney were reported for the first time yesterday in The New York Times, which anonymously cited lawyers connected to the investigation. They seem to contradict testimony given by Mr Libby to a grand jury that he had learnt of Ms Plame from journalists.
According to the newspaper, the notes from Mr Libby are a record of a conversation with the Vice-President that took place on 12 June 2003, weeks before Ms Plame's name first appeared in a column written by the prominent journalist Robert Novak. Mr Fitzgerald will this week conclude his investigation into whether anyone at the White House deliberately unmasked Ms Plame to journalists in 2003 as part of a vendetta against her husband, Joseph Wilson, who had been questioning administration claims regarding weapons of mass destruction in Iraq.
It is clear that if anyone at the White House is charged by Mr Fitzgerald, they would have to resign at once. No one knows what Mr Fitzgerald will decide, but he is expected to end the suspense before Friday. Mr Libby is widely considered to be at risk, as is Mr Bush's top political confidant, Karl Rove.
If, indeed, Mr Cheney was the first to mention Ms Plame to Mr Libby that does not suggest any criminal wrong-doing on his part.
Mr Cheney may not have known at the time of Ms Plame's status at the CIA as an undercover agent.
Disclosing the name of a covert agent, if done knowingly, is a crime. Moreover, a vice-president is perfectly at liberty to discuss all secrets of state with his own chief of staff.
Yet, the latest twist turns up the heat on the White House, because it indicates that Mr Cheney was personally involved in the effort to find out more about Ms Plame at a time when the White House was fuming about her husband's revelations about WMD and the increasingly limp-looking case for war in Iraq.
Mr Wilson had been sent by the CIA to Niger the year before to seek evidence that Iraq had tried to buy uranium there for its weapons programme. He found no such evidence, yet the Niger link was cited by President Bush in his 2003 State of the Union speech. Mr Wilson thereafter began to accuse the White House of twisting the facts on Iraq.
Mr Wilson finally went public in July 2003 in an article in The New York Times.
While no one doubts that the White House took aggressive steps to counter the impact of Mr Wilson's criticism, it is up to Mr Fitzgerald to decide whether that included the illegal leaking of his wife's name. At the same time, however, he may be tempted to file criminal charges against anyone in the White House he believes either lied to his grand jury or tried to obstruct justice in the case.
This may be the biggest danger for Mr Libby, who may have decided to omit any mention of Mr Cheney in his grand jury testimony because of a desire to protect him. The Times said that Mr Cheney had himself heard about Ms Plame from the former director of the CIA, George Tenet. Neither the Vice-President's office nor lawyers for Mr Tenet were offering any comment yesterday.