Fifty years ago Saturday, President Lyndon Baines Johnson shocked the world by withdrawing from the 1968 presidential campaign. Johnson was an unparalleled political junkie, and his persuasive manner and commitment to activist government had defined Washington for decades, ever since the gangly, ambitious Texan arrived in the nation’s capital as a congressional aide in 1931. Then, amid the stalemated war in Southeast Asia, Johnson claimed he must devote all of his time to Vietnam without sparing a moment to win reelection.

Of course, Johnson’s decision also stemmed from less noble motivations. His approval rating in the Gallup poll had sunk to 36 percent, the upstart campaign of antiwar senator Eugene McCarthy had nearly upset the incumbent president in the New Hampshire primary, and hated rival Robert F. Kennedy had entered the race. Worse yet, Johnson had become a lightning rod for discontent. Everywhere he traveled in 1968, protesters met him with a stinging chant: “Hey, hey, LBJ, how many boys did you kill today?”

Unpopularity drove Johnson out of office. But in recent years, his fortunes have shifted, as memories of the war have ebbed and corrosive national politics have made Americans yearn for the days of an effective president capable of seminal achievements that positively influence their lives.

Johnson’s unpopularity extended beyond his tenure in the White House. In the last four years of his life (Johnson died in 1973), the former president, whose legislative skills made him famous a decade earlier, was seen as a liability instead of a political asset.

In 1972, Democratic leaders warned Johnson to stay away from the party’s national convention in Miami, and the week-long festivities barely took note of the party’s onetime champion. Johnson, former aide Jack Valenti complained, had become “a non-person, expunged from the Democratic Party with the same kind of scouring effectiveness that Marxist revisionists use to rewrite Communist history.” As a final petty insult, the managers of the convention made sure Johnson’s picture was absent among the portraits of former standard bearers Franklin D. Roosevelt, Harry S. Truman, Adlai Stevenson and John F. Kennedy. ...