Well, not seriously, but yes the idea has floated around. I had no idea, but I did research into it, and here's what I found:

' More ominous- ly, for the second time in less than two decades, Washington began to give serious consideration to using atomic weapons in order to win a war in Indo-China. In July 1969, Nixon decided to "go for broke" and "attempt to and the war one way or the other-either by negotiated agreement or by an increased use of force!'52 At the behest of the president, National Security Council (NSC) advisor Henry Kissinger directed the NSC to undertake a top-secret study for a proposed escalation of the war into the north. This study, code named 'Duck Hook', proposed saturation bombing of the main population centres, mining of harbours and rivers, bombing of the dike system, a US troop invasion, the possible use of nuclear weapon?to destroy strategic passes along the Ho Chi Minh Trail, and the bombing of North Vietnam's most important rail links with China. "There was:' writes Seymour Hersh in his exhaustive and definitive study of Nixon-Kissinger foreign policy, "a separate, even more secret study dealing with the implications of using tactical nuclear weapons on the rail lines, the main funnel for supplies from the Soviet Union as well as China". Kissinger told his NSC staff members analysing the 'Duck Hook' pro- posals that they were "to examine the op- tion of a savage, decisive blow against North Vietnam" which should not exclude the use of nuclear weapons.53 By early 1971, the consideration of.the nuclear option and the possible use of tactical nuclear weapons in Vietnam had become a common topic of discussion bet- ween Nixon and Kissinger. According to some of the NSC advisor's aides, the ad- ministration's two senior foreign policy- makers pefsisted with this kind of talk for the duration of the Nixon presidency.54 Although the White House did not move the discussion from the planning to the opera- tional stage, and although the president described the threats of nuclear intervention as part of a grand strategy to terrorise the North Vietnamese to come to the conference table (Eisenhower's approach to North Korea and what Nixon termed 'the madman theory'), there was a dramatic shift in US policy toward Vietnam beginning' in 1969. At its core was the idea of using nuclear weapons to defeat a national liberation movement in the third world. There was a real threat of the use of nuclear weapons in Vietnam and, in fact, there is evidence of at least one nuclear alert that took place between late 1970 and early

1971. According to a CIA official serving in agency's operation centre during this period, the Air Force issued a top-secret 'stand down' order 'forbidding all intelligence and other operations in and over the area of North Vietnam! The official continued: 'A stand-down did exist and it's a standard in- dicator for a nuclear attack. . .'55 The con- sequences of such an attack could have been a global nuclear confrontation if, as was like- ly, the Soviet Union had come to the aid of its Vietnamese ally. ^^1

Basically, Nixon got so fed up with the war and lack of progress that he asked Kissinger to investigate, and Kissinger did without ruling out nuclear weapons, and there's evidence that a nuclear alert might have even happened. However, it never did, likely because the Soviet Union would've reacted very harshly, and the US wanted to avoid a global confrontation.

Another article on the subject ^^2 , suggests that while Nixon and Kissinger did make vague threats and explorations of the possibility, they never did come close to using them (Kennedy and Johnson never even considered it, reportedly). The risk of escalation was apparently too much, and though some argued that the Soviet Union wouldn't get involved, there were fears China would, and that fighting China with nuclear weapons (which would likely be required) would then provoke the Soviet Union. Nixon did state in an interview in 1985 that he considered the use of nuclear weapons 4 times in his administration, and one was to end the Vietnam War. Kissinger disagreed, saying there was never a serious consideration of the possibility of using nuclear weapons (he said this in a separate interview).

So while it's argued whether or not it's considered, how "close" the US came to using them is clear: the US stayed very, very far from actually using nuclear weapons. Some argue that's because of the world public opinion, some because of global confrontation that would inevitably follow, and some because of the moral implications of such an attack (and how it would be perceived to be a form of "we can nuke anything non-white", even), and maybe it was all three. Either way, while Nixon says he considered it, most people disagree that he ever did or that he ever expressed that consideration, and from what I've seen it doesn't appear anyone ever "seriously" considered using nuclear weapons.

^^1 Nuclear War and US-Third World Relations: The Neglected Dimension James Petras and Morris Morley Economic and Political Weekly, Vol. 23, No. 4 (Jan. 23, 1988), pp. 151-153+155-158

^^2 The Nuclear Taboo: The United States and the Normative Basis of Nuclear Non-Use Nina Tannenwald International Organization, Vol. 53, No. 3 (Summer, 1999), pp. 433-468

Eisenhower certainly considered using them. This is a fun topic for any historian who deals with Eisenhower because there is a nice division in the historiography between those who think he was seriously considering using them to help the French at Dien Bien Phu, and those who think he never would have. I'm on the side that takes Ike's numerous, private musings, that nuclear weapons in a battle situation should be used like any other weapon (*like a bullet) seriously. Others think Eisenhower never intended to use nuclear weapons, and I honestly have a hard time accepting that line of thinking since it essentially ignores Eisenhower's very stark and quite clear thinking on the Cold War.

So yes, Eisenhower and Dulles seriously considered using nuclear weapons in Vietnam.