Opinion | L.B.J. Did It in 1968. Biden Can Do It, Too.

On March 31, 1968, Lyndon Johnson used a nationally televised address from the Oval Office to announce that he would no longer seek, and would not accept, his party’s nomination for the presidency of the United States.

After his catastrophic performance at last week’s debate, President Biden is under growing pressure to do the same. It’s tempting to think of the comparison as pure political tragedy: two proud men coming to the end of their often-distinguished careers, forced to face that they were deeply wounded candidates heading toward humiliating defeats they could avoid only by surrendering the second terms they were sure they deserved.

To see the moment only in those terms, though, misses the importance of what Johnson did in 1968. Yes, his candidacy had been severely damaged. His decision to drop out of the campaign was tangled up in all sorts of political, psychological and emotional issues. What is forgotten about Johnson’s decision is the number of other factors the president was weighing.

More than anything else, he was hoping that by ending his campaign he could defuse an existential threat to the nation. The details may be different, but that’s the situation Mr. Biden is facing, too.

Johnson’s crisis started on Jan. 30, 1968, when the North Vietnamese military broke the Vietnam War’s annual New Year cease-fire with a surprise assault on almost every strategic site in South Vietnam. Analysts would later say that the United States’ counterattack turned the Tet offensive into a rout. But that wasn’t clear at the time. It took 12 days for American and South Vietnamese troops to drive the North Vietnamese out of Saigon’s Cholon district and over a month for them to reclaim the coastal city of Hue, at a casualty rate higher than the Americans had suffered at any previous point in the war.

Then the crisis deepened. On Feb. 27, 1968, the Joint Chiefs of Staff formally requested that Johnson increase the troop deployment in Vietnam to 700,000 soldiers, a 40 percent increase over the half-million already there. For almost two weeks, Johnson’s advisers fiercely debated a potential escalation. On the 13th day — March 10 — news of the request leaked and led to a firestorm of criticism from the Democratic Party’s antiwar wing. Two days later, the wing’s only presidential candidate, Senator Eugene McCarthy of Minnesota, took 42 percent of the vote in the New Hampshire primary, surprisingly only eight points behind Johnson.