The intervention took place a couple of weeks before the '68 election--LBJ had already said he would not run, the Reps. had already chosen Nixon and the Dems. had chosen Humphrey. Nixon won the election 43.4% to 42.7% (Wallace got 13.5%).

Nixon intervened by getting Madame Chennault, a very influential Chinese national, widow of a US WW II air ace, to convince the SVN delegation that they could get a better deal under Nixon than they would from the negotiations that LBJ was overseeing.

Article here. There's speculation in the article about why LBJ didn't make the "treason" public.
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