LBJ tells Dirkson that someone on Nixon's campaign, (maybe Laird or Mitchell)
is making representations through an intermediary ("the old China crowd", meaning
Chinese govt in exile, Taiwan, Anna Chenault)
Described here in Baltimore Sun.
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The Nixon campaign feared that Thieu's presence would result in a deal that would end the war and swing the election to Humphrey. President Lyndon Johnson had ordered a halt in the bombing of Hanoi, also raising those hopes. But when Thieu indeed stayed away, the talks collapsed and Nixon was elected by 0.7 percent of the vote.
At the time, Humphrey had received from LBJ surveillance by the FBI of Chennault visits to the South Vietnamese Embassy in Washington to urge Thieu not to go to the Paris meeting. The FBI reported she had gone to the embassy, then to the Nixon campaign headquarters and back to the embassy. But Humphrey declined to make the information public, knowing it was classified, and he incredibly doubted Nixon would be capable of engaging in such a nefarious undertaking.
In Humphrey's later memoir, he wrote: "I wonder if I should have blown the whistle on Anna Chennault and Nixon. He must have known about her call to Thieu. I wish I could have been sure. Damn Thieu. Dragging his feet this past weekend hurt us. I wonder if that call did it. If Nixon knew. Maybe I should have blasted them anyway."
LBJ aide Joe Califano later said Humphrey's failure to use the intelligence on Chennault "became the occasion for a lasting rift" between Johnson and his vice president. "That refusal really tore it," Mr. Califano told me. "Johnson thought Hubert had no balls, no spine, no toughness." LBJ himself told Senate Minority Leader Everett Dirksen he considered Nixon's actions an act of "treason," as a possible violation of the little-known Logan Act forbidding individual citizens to inject themselves into the conduct of foreign policy.
http://www.baltimoresun.com/news/opinion/oped/bs-ed-op-0410-witcover-chenault-20180406-story.html