Lyndon Johnson, shown in this August 1972 photo from the LBJ Presidential Library.

It is 4:46 p.m. on Jan. 2, 1973, and Lyndon Johnson speaks to Richard Nixon for the last time ever. Nixon calls LBJ at the Ranch to report that peace in Vietnam is near, urges him to use his house in Key Biscayne, Fla., where their mutual friend Bebe Rebozo lives, and ascertains that Johnson will not be attending a Washington memorial service for Harry Truman, who had died a week earlier. Johnson says that on the day before, New Year’s day, he yelled too much at the University of Texas football game, and as a result, had to summon doctors because “I had heart pains all night.” Reproaching himself, Nixon says, “I called you at the wrong time!”

Listen to the conversation here:

Forty years ago this month, Lyndon Johnson was agonized to know that Americans thought of him as the architect not of equal rights and Medicare but the hated Vietnam War. Feeling like an unappreciated outcast, the ex-president, often depressed, repeatedly listened to Simon & Garfunkel’s “Bridge Over Troubled Water.” It sounds incredible that LBJ should be attracted to that anthem by the passionately antiwar singers, until you remember the lyrics: “When you’re weary, feeling small, when tears are in your eyes… And friends just can’t be found…”

Johnson had suffered three major heart attacks and knew he did not have long to live. He incessantly recalled that Johnson men died before reaching 65 years old, and he was 64.

In December 1972, Johnson called civil rights leaders to his new Presidential library in Austin, Texas, to commemorate his landmark Civil Rights, Voting Rights and Fair Housing Acts. Suffering severe heart pains and startling the audience by popping a nitroglycerin capsule into his mouth, he lamented that he hadn’t “done enough” to advance equal rights and closed by repeating the peroration of his famous 1965 speech to Congress, “We Shall Overcome!”

On Jan. 12, 1973, ten days before his death, Johnson summoned Walter Cronkite to the LBJ Ranch and, before CBS cameras, recalled his own transformation from a Senate candidate who had virtually endorsed white supremacy into the second greatest civil rights President of all time. Cronkite did not know that this would be LBJ’s last interview — he should have paid more heed to Johnson’s chatter about selling land and cattle (to minimize death taxes) and his obsessive smoking (LBJ claimed to Cronkite that it was better for his heart for him to smoke than for him to be nervous).

Lyndon Johnson spoke to Walter Cronkite, left, at his ranch near Stonewall, Texas, ten days before his death in January 1973. Photo by CBS

Johnson was napping in his ranch bedroom when he suffered his last massive coronary, called his beloved Secret Service agent Mike Howard and fell to the floor, almost instantly dead. It was exactly two days after the presidential term he would have served, had he run again in 1968, and almost the same moment that his successor, Richard Nixon, declared a peace in Vietnam that had eluded LBJ and would not last.

After Johnson’s first heart attack in 1955, doctors had told him that if he ever started smoking again, he would kill himself. But almost as soon as he left the presidency, he resumed fierce chain smoking, overeating, and, sometimes, overdrinking. Some of his aides privately muttered that the boss was committing slow motion suicide. But when one of his horrified daughters begged him to stop the cigarettes, Johnson shook his head and exclaimed, “No, I’ve raised you girls, I’ve been president, and now it’s my time!”

Michael Beschloss is a PBS NewsHour regular and can be reached on Twitter at @BeschlossDC.