I'll have to re-read a bunch of stuff (most of which I have loaned out to friends, never to be seen again)to get my facts straight.
"Wilson told the President, over the telephone, that he had just received a report on Oppenheimer. It consisted of a letter from William Borden, the former director of the Joint Congressional Committee on Atomic Energy, to the Secretary of Defense. Borden charged that it was "more likely than not that J. Robert Oppenheimer is a Communist spy."
I'd have to poke around other sources to check it out thoroughly. Ambrose was a big lefty and may have covered for Oppenheimer in this book.
Wilson is Charles E. Wilson, Ike's Secretary of Defense.