On the night of March 31, 1968, President Lyndon B. Johnson rocked the political world with these words concluding his televised remarks from the Oval Office:

“With American sons in the field far away, with America’s future under challenge right here at home, with our hopes and the worlds’ hopes for peace in the balance every day, I do not believe that I should devote an hour or a day of my time to any personal partisan causes or to any duties other than the awesome duties of this office, the presidency of your country.”

He went on: “Accordingly, I shall not seek, and I will not accept, the nomination of my party for another term as your president.”

At that moment, as a political reporter, I was covering a Democratic campaign rally by Sen. Eugene McCarthy of Minnesota at Carroll College in Waukesha, Wis. He was winding up a speech of his own in his effort to dump LBJ from that office in the state’s approaching primary. When the news hit McCarthy, he broke off and returned to his campaign offices in Milwaukee to consider his next move. We reporters hastened to follow him there.

He told a friend at the time: “I feel as if I’ve been tracking a tiger through long jungle grass, and all of a sudden he rolls over and he’s stuffed.” He subsequently told us that Johnson “now has cleared the way for the reconciliation of our people.”

Asked whether he now believed Vice President Hubert Humphrey would step in as the party establishment’s candidate, McCarthy wryly replied that he didn’t know, “but I think if you look closely, you might see a slight cloud on the horizon tomorrow morning.”

At the same time, Sen. Robert F. Kennedy of New York, who had lately joined the race against LBJ, was flying east from Arizona, and when his plane landed at Kennedy Airport in New York, the state’s chairman, John Burns, rushed aboard, telling him: “The president is not going to run!” Kennedy, rising from his seat, fell back in astonishment at the news.

After conferring briefly aboard with Burns and chief campaign strategist Fred Dutton, RFK walked through the terminal as a woman screamed to him: “You’re going to be our next president!” Grim-faced, he made no reply.

But in the car going to Manhattan with Dutton, his wife Ethel and Los Angeles Times reporter Dick Dougherty, Kennedy final broke the silence. “I wonder,” he mused, “if he’d have done this if I hadn’t come in.”

Johnson’s electric decision immediately transformed the 1968 presidential campaign. McCarthy, who had almost upset LBJ in the kickoff New Hampshire primary, proceeded to beat a Johnson stand-in in the Wisconsin primary. Thereafter, Kennedy set off on a winning streak of other state primaries broken only by a loss to McCarthy in Oregon, and on into California for a showdown with McCarthy, and with Humphrey as well, which Kennedy later would win.

The year 1968 was later called in a book “The Year the Dream Died,” in part because Dr. Martin Luther King Jr. was assassinated in Memphis on April 4 and Robert Kennedy two months later in Los Angeles. The year dealt a bitter blow to the civil rights movement that both men urgently and steadfastly embraced; and to liberalism in general.

Compounding the grief of both constituencies was the resulting election of Republican nominee Richard Nixon, long their bete noire. He went on as president to sustain the war in Vietnam that Johnson had failed to end, and then he saw his country suffer humiliating defeat there after his own ignominious resignation in disgrace.

Had Lyndon Johnson not made that unexpected decision against seeking re-election in 1968, there is no telling now how the year would have run its course, leaving many what-ifs in its wake. All that can be said half a century later is that we may not see anything like that again.

We can only hope so, in another time when other dreams seem in peril under an uncommonly unpredictable, lying and reckless president.

Editor’s note: Jules Witcover’s latest book is “The American Vice Presidency: From Irrelevance to Power,” published by Smithsonian Books. You can respond to this column at juleswitcover@comcast.net.