The 1968 reevaluation of the conduct of the war in Vietnam was conducted for legitimate reasons having little or nothing to do with domestic politics per se.
In a democratic system, every action by an elected official, especially a first-term president, is viewed through the prism of elective politics. And 1968 was certainly a turbulent period in U.S. political history with much at stake in the upcoming presidential election. But Lyndon Johnson had very real reasons for ordering a reevaluation of the situation in Vietnam. And, it should be noted, that Johnson was clearly contemplating -- if he had not already decided -- not to run for reelection, a decision he publicly announced on March 31 of that year.
Nineteen sixtyeight began with perhaps the most decisive and misunderstood event in the entire war: the Tet Offensive. While the United States and its South Vietnamese military allies prevailed over the Viet Cong -- in fact, the Viet Cong never recovered from the devastation to its infrastructure that followed the offensive and ceased to be an effective insurgency -- public perceptions in the United States were that the Tet Offensive marked a resounding defeat for the United States and the Republic of Vietnam. Caught off-guard by the timing and scale of the Viet Cong offensive in the heart of the south's major cities, the U.S. and South Vietnamese Governments were extremely embarrased.
Another major event that occurred early in 1968 was the North Korean seizure of the U.S.S. Pueblo, a U.S. Navy intelligence ship that was sailing off the Korean coast and was unable to defend itself against the North Korean naval attack. Both incidents were seen around the world, and certainly here at home, as highly visible symbols of American incompetency.
In the context of the time, with the divisiness of the war in Vietnam here in the United States, the emotional impact of the Pueblo's seizure, the political and social turbulence raging across American cities, and Johnson's increasingly pessimistic prognostications about his own presidency, the time was inarguably right for a fundamental reevaluation of the U.S. role in Vietnam.
Could domestic political considerations have played a part in the decision to conduct the reevaluation? Certainly. But the psychological trauma in Washington, D.C. following the Tet Offensive combined with the Pueblo seizure created the foundation upon which a reassessment was fully warranted.