Nixon would seem to have wanted to go with his plan of giving control of the war to the South Vietnamese, it might not have seemed that bad save until the end. Afterall Humphrey kinda underestimated the North Vietnamese willingness to fight, since reports from Abrams were pretty good, President Thieu was doing just fine pacifying things but still needed our troops against their last hurrah in 75. Don't know if Nixon would have done the damage control on the Tet Offensive since it only looked shocking, we wiped basically those commie bastards out.
We might have seen an entirely Red Vietnam, granted even they provided help against the Chinese proxies in Cambodia.