A new book called Chasing Shadows goes into the matter in depth. There isn't any question Nixon did this; the only questionable part is whether this was the reason Nixon engaged in a series of elaborate coverups throughout his presidency. I think those coverups were simply a result of his paranoia and hatred, and those character flaws were what ultimately did him in. Furthermore, subverting the Paris talks was yet another manifestation of his paranoia.
Taut and laden with touches of humor, “Chasing Shadows” mainly seeks to highlight the importance of the Chennault Affair to Nixon’s undoing. What was the Chennault Affair? Late in the 1968 presidential campaign, President Johnson, having forsworn another term, was ready to halt the bombing of North Vietnam to try to revive peace negotiations. Nixon, the Republican nominee, considered the decision a ploy to help Vice President Hubert Humphrey, the Democratic candidate, who was trailing in the polls. So Nixon had his law partner (and later attorney general) John N. Mitchell speak to Anna Chennault, a 43-year-old Chinese-born Republican activist, who in turn spoke to Bui Diem, the South Vietnamese ambassador, who in turn told South Vietnamese President Nguyen Van Thieu to reject LBJ’s initiative, promising a better deal once Nixon was elected. This skulduggery arguably violated the Logan Act, which bars private citizens from freelancing in foreign policy.
In implicating Nixon in this episode, Hughes adduces a great deal of strong evidence, including from LBJ’s own White House tapes (yes, he made them, too — though not nearly as many as Nixon). Roughly the first third of “Chasing Shadows” meticulously maps out the twists and turns in the bombing-halt negotiations, creating a delicious portrait of pervasive suspicion among Nixon, Johnson, Humphrey and their aides. Hughes establishes that as soon as Nixon came into office, he knew he had a big secret to hide.
Hughes then shows how this secret contributed to Watergate. Told by FBI Director J. Edgar Hoover in late 1968 that the bureau had bugged his campaign plane (a falsehood, Hughes says), Nixon decided he needed his own dirt on LBJ. After taking office, he assigned H.R. Haldeman, his top aide, to gather intelligence from across the government to show that LBJ had acted to help Humphrey. Haldeman delegated the task to a young flunky named Tom Charles Huston.
The book might be worth checking out.
Incidentally, as of the date of this blog post, Anna Chennault is still alive. She is 89 years old.