This scenario bodes for far more then the 1972 Election, Rockefeller Republican, the ramifications of allowing Operation Duck Hook could have led to World War III. The usage of mines in Haiphong Harbor, the expansion of the war into the North and the usage of an atomic bomb without a major North Vietnamese offensive would destroy America’s “moral standing” in the war, if it ever had any to begin with.
The man in charge of arranging Operation Duck Hook, Captain Rembrandt C. Robinson, had warned the Joint Chiefs of Staff in January 1969 that an operation like “Duck Hook” would destroy the image of the U.S. as peaceful liberators of South Vietnam, and more like belligerent destroyers of the North. However, had Duck Hook been embraced by Nixon-Kissinger, then the whole character of the war would change dramatically. The mining of Haiphong Harbor would have happened before the massive North Vietnamese Easter Offensive in 1972 when the war was seen as a battle for South Vietnam and not against the North Vietnamese. Nixon’s statement, “The greatest title history can bestow is the title of ‘peace maker’,” would have been seen as a joke by the world community, and thus Kissinger’s “Shuttle Diplomacy” and “Ping-Pong Diplomacy” and what have you diplomacy with China would never have happened.
Secondly, Captain Robinson warned that the “nuclear option” could spark off a war with the Soviets. While we can never be sure if Nixon wanted to use the atomic bomb on Hanoi, in your scenario he does. You can be sure Brezhnev would not have taken this sitting down. After all, Hanoi was filled with Soviet “military advisors” and weapons, a destruction of these people and supplies could be seen as an act of war. Especially after an “unprovoked” mining of Haiphong Harbor, where Soviet ships were harbored, an attack on Hanoi could have provoked World War III. “We’re walking on atomic eggshells,” was one comment Nixon had told Melvin Laird in 1969, and he was right. While an atomic bomb may have ended the Vietnam War, it very well could have begun the Third World War.
As for the 1972 Election, Nixon would not be as dead of a duck as he may seem. After all, blue collar America would still be with him. “Nixon got the Commies” is what the Archie Bunkers would be saying, and these New Deal Democrats were who Nixon had to win to beat the New Leftist George McGovern. Without Nixon in China, McGovern would have been able to paint him as a flip-flopper on peace in Vietnam, but in the end it was Nixon who brought the Vietnam War to a close, even if it meant dropping an atomic bomb. In short, a Scoop Jackson, Hubert Humphrey, Reuben Askew, Vance Hartke, Terry Sanford, Wilbur Mills or even George Wallace nomination could have won the White House for the Democrats, but McGovern just isn’t presidential timber. Nixon’s win is underwhelming and unimpressive, as the Democrats gain more than 65-seats in the Senate and come close to a 2/3rds majority in the House:
Richard Nixon/Spiro Agnew (R): 337 EV; 53.6% of the PV George McGovern/Thomas Eagleton (D): 201 EV; 43.4% of the PV 
