I mean what if Chairman Mao had halted Chinas support for North Vietnam at an early stage? Lets say 1970? To piss-off the USSR, and handed the US possibly a better end to the Vietnam war? and thusly having an earlier opening with the US?
The war goes better after 1970. I don't think it makes the war more popular. n Nixon still works for a deal. a At the very least there are fewer communist forces in South Vietnam when the peace is signed. I don't think that buys them that much more time.