The cultural divide that opened that school year on California campuses forever changed some young men. The new Stanford student president, David Harris, was later imprisoned for refusing military service. Some freshmen in Mr. Romney’s dormitory, Rinconada Hall, joined an antiwar commune or fought the draft as conscientious objectors.

Mr. Romney, though, stayed true to his chinos and the Vietnam War, even joining a counterprotest against the occupation of the office of the university president, Wallace Sterling. Forty-six years later, some classmates remember his pro-war stand as principled and heartfelt; others say he merely championed the worldview of his father, George Romney, then Michigan’s governor, a war supporter and a future contender for the 1968 Republican presidential nomination. Still others say he sailed through the most schismatic moral and political issue of that time — and perhaps of any period since in the United States — with neither much angst nor introspection.

On his own for the first time, Mr. Romney finished his freshman year as he began it: conventionally patriotic and faithful to the traditional values of the time. “He was loyal to his family beliefs, his church beliefs and his country’s beliefs without trying, really, to understand what qualifications they had,” said Karl Drake, another Rinconada freshman and an antiwar activist who sometimes clashed with Mr. Romney.

It is unclear whether Mr. Romney’s hawkish Vietnam stance in 1966, when he was 18 years old and first exposed to the larger world, presaged his hawkish foreign policy stance as a presidential candidate in 2012, in which he has promised more confrontational approaches toward China, Iran and Russia than those adopted by President Obama. But just as Mr. Romney’s views on some other issues evolved over the years, his public assessments of the Vietnam War shifted markedly.

His pro-war sympathies at Stanford changed four years later, when he recanted and called the war a mistake. After saying in an interview during his failed bid to unseat Senator Edward M. Kennedy of Massachusetts in 1994 that he had no interest in military service as a youth, Mr. Romney said in 2007 during his first run for the Republican presidential nomination that he had sometimes longed to join the troops in Vietnam.