Nearly all the obituaries for Eugene McCarthy credit the former Minnesota senator with forcing Lyndon B. Johnson out of the 1968 race for the Democratic presidential nomination. Without taking anything away from McCarthy's principled run against a sitting president of his own party, this is simplistic history that ignores everything we have since learned about that fateful year.

To be sure, McCarthy added to Johnson's sense of beleaguerment when the little-known senator unexpectedly garnered 42 percent of the vote in the New Hampshire primary. Johnson had talked about quitting months earlier. He was exhausted by the burdens of office, especially the Vietnam War, and worried about his ability to survive another term.

The Tet offensive by communist forces in South Vietnam, while a defeat for Hanoi, was particularly debilitating. It gave lie to Johnson's claims of steady progress in the war and was undoubtedly a decisive factor in McCarthy's strong showing on March 12. Before the offensive, polls indicated that Johnson was going to annihilate McCarthy.

Johnson did not announce his withdrawal the day after the primary. Indeed, political soundings taken soon afterward showed that he could still win the nomination, and Johnson was convinced that if he was renominated, he would be re-elected. To some degree, Johnson relished the prospect of running against the liberal intelligentsia in his party, an element he had courted but one that had never truly accepted him.

So what precipitated LBJ's withdrawal on March 31?

The only event of significance between McCarthy's unexpected showing and Johnson leaving the race was Robert F. Kennedy's entry. RFK announced his candidacy on March 16, after refusing to challenge Johnson earlier because he reportedly feared that it would be perceived as a personal vendetta. But after New Hampshire, Kennedy could plausibly claim that the Democratic Party was deeply split over the war.

Much of the media treated Kennedy's entrance as proof that Johnson was unlikely to be renominated. But as any hard-boiled, vote-counting politician would have realized on March 16 — and Johnson was among the best — RFK's entrance enhanced Johnson's chances. In 1968, delegates were largely controlled by elected officeholders and party bosses. And because McCarthy deeply detested Kennedy and was not about to withdraw or join forces with him, a three-way race meant the anti-war faction of the party was irrevocably split between two Catholic liberals. As The New York Times reported on March 24, LBJ seemed likely to get at least 65 percent of the delegates for the nomination.

Nonetheless, it was Kennedy's entrance that was the precipitating factor in Johnson's withdrawal. Johnson believed, and with good reason, that he had always kept faith with the 1960 compact he had formed with John Kennedy, when LBJ stunned most observers by giving up the Senate to run for vice president. In return for subordinating himself to a senator who was clearly his political junior, Johnson was given the opportunity to be on a national ticket and thereby transcend the onus of being a Southerner, perhaps the last political vestige of the Civil War. If he ran well, LBJ could keep alive his burning desire for the presidency — in 1964, if the JFK-LBJ ticket lost, and in 1968 if Kennedy served two terms.

Instead, of course, Johnson was abruptly catapulted to the White House in 1963. He was then treated, first by RFK, as a usurper, grabbing at the accoutrements of power, and then later by the country as an unworthy successor, even though Johnson had done far more to advance liberal causes than JFK had.

The flaw in Johnson was that he was not content to lead and be respected. Rather, he demanded almost slavish support and public adoration. Such deep emotion is reserved for very few presidents, and usually they have to die in office to achieve it. Johnson's curse was that he inherited the presidency from such a man. And now RFK was repudiating everything Johnson represented or hoped to accomplish.

As Johnson told his biographer, Doris Kearns Goodwin, after he left the White House: "I felt (in 1968) that I was being chased on all sides by a giant stampede coming at me from all directions . ... And then the final straw. The thing I feared from the first day of my presidency was actually coming true. Robert Kennedy ... openly announced his intention to reclaim the throne in the memory of his brother. And the American people, swayed by the magic of the name, were dancing in the streets. The whole situation was unbearable for me."

If McCarthy cannot be credited with forcing Johnson from the race, the meaning of his challenge to LBJ is hardly diminished. It was McCarthy's candidacy that cracked open the Democrats' consensus on foreign policy. Nearly four decades later, the party is still struggling with that divide.

Max Holland is the author of "The Kennedy Assassination Tapes." He wrote this commentary for the Los Angeles Times.