Arriving at the Lyndon B. Johnson Presidential Library in Austin, Texas, Monday President Biden hopes to revisit the mountaintop of LBJ’s greatest achievement: passage of the 1964 Civil Rights Act.

Biden will be commemorating the landmark legislation, which took effect 60 years ago this month, outlawing discrimination on the basis of race, color, religion, gender or national origin.

The zenith of the civil rights movement, at least to that time, the 1964 act ended the “Jim Crow” era of legal segregation and the denial of public accommodations. It had passed the House in February of that year and been subjected to months of filibuster in the Senate, much like predecessor civil rights bills had been in 1957 and 1960, when Johnson was Senate majority leader.

Those bills had been watered down to accommodate segregationist Southern senators in Johnson’s own Democratic Party. But in 1964, LBJ was in the White House and he had a more unified party and better support from Senate Republicans. After 60 days of debate, the necessary two-thirds of majority required for cloture in that era was achieved. Nine days later, the bill was passed by a vote of 73-27.

In originally scheduling Biden’s visit to Austin, the White House surely intended to highlight that milestone and the Democratic Party’s commitment to it.

But much of the coverage of today’s Austin event is likely to highlight another link between Biden and LBJ. Both men brought an end to their presidencies by declining the nomination of their party for another term. And unlike incumbent presidents who declined to seek a term they could have pursued (Harry S Truman in 1952, Calvin Coolidge in 1928, Theodore Roosevelt in 1908), Biden and LBJ did not take themselves out of the running until the nominating process was well along.

LBJ made his stunning announcement in an Oval Office address during prime time on the night of March 31, 1968. Johnson was then in the final year of his one elected term in office, having previously served out the unexpired term of his assassinated predecessor, John F. Kennedy.

Johnson had won his full term in a historic landslide with more than 60% of the popular vote.

Bolstered by huge majorities in Congress carried in on his coattails, LBJ would have a series of triumphs in the following year, enacting Medicare and a landmark immigration bill in addition to a raft of new social programs attacking income inequality. But all of this “Great Society” legislation would share the stage with Johnson’s equally consequential commitment to escalating the U.S. role in Vietnam.

In 1964, perhaps fearful of electoral consequences if South Vietnam fell to communist insurgents and invaders from North Vietnam, LBJ got Congress to back the open-ended war authority of the Gulf of Tonkin Resolution. On July 28, 1965, he raised the U.S. troop commitment from 75,000 to 125,000 and doubled the size of the draft. Eventually there would be half a million Americans in uniform in Southeast Asia, dividing Americans on the home front as no war had since the 1800s. LBJ’s domestic agenda was more popular but did not stem the tide of urban unrest that plagued the summers of 1965 and 1967.

By the spring of 1968, Johnson’s polling numbers had collapsed, falling below 40% for the first time. A challenge to his renomination emerged from little-known Minnesota Sen. Eugene McCarthy, almost entirely as a Vietnam War protest. When McCarthy put up respectable numbers in the New Hampshire primary, New York Sen. Robert F. Kennedy, brother of John Kennedy, also entered the primaries. Polls showed he might be formidable.

Yet in that era, primaries did not choose most of the delegates to the nominating convention. Most were chosen by state party chairs, big city mayors and other elected officials with intraparty clout and deep ties to the hierarchy. LBJ might still have gotten the nomination that year, but instead, LBJ stunned the party by standing down in March.

His inner circle of staff urged him to carry on, but his family and some trusted intimates were ambivalent at best. Although it was not well known at the time, historians have since detailed the degree to which LBJ had complained of exhaustion. Although not yet 60 years old, LBJ had survived an earlier heart attack and was being treated for other ailments as well. He would die at 64 in January 1973.

Issues of age, vitality and mental acuity

That was the same month a young Joe Biden first took the oath of office as a U.S. senator. Now, at 81, the issues of age, vitality and mental acuity had been front and center for weeks if not months before he stepped aside on July 21.

If LBJ was still a contender for the nomination when he quit, Biden was the all-but-certain nominee this month when he did the same. With all delegates chosen for the August convention in Chicago (a return to the city and month of the 1968 convention), 90% were committed to Biden.

Another point of similarity between LBJ and Biden is their shared history as vice presidents who made way for vice presidents. LBJ had been selected by JFK in 1960 despite significant differences and a lack of personal rapport that extended to the staffs of the two men. Yet the Texan was able to carry his home state in November and thereby put the ticket over the top in the Electoral College.

Biden, too, was a somewhat unlikely pairing with Obama in 2008 and a surprise to many of Obama’s admirers. Biden had been cool and even condescending toward Obama in some campaign events, referring to him at one point as “exceptionally clean and articulate” – a description some in Obama ’s camp considered condescending and even racist.

But Biden had ended his own bid for the presidency early in 2008, leaving time for him to mend fences and for Obama to see what Biden’s blue-collar background and appeal to white working class voters might bring to the ticket. Although harder to quantify than the LBJ contribution, Biden did his part and played the loyal No. 2 fully through the next eight years.

In yet another parallel, LBJ’s sudden exit served to elevate his vice president, Hubert H. Humphrey, the former senator from Minnesota. Humphrey was a longtime champion of civil rights and the labor movement, and he made steady progress through that fall campaign against Republican Richard Nixon. Some believe that if the Vietnam peace talks LBJ pressed for on Vietnam had not stalled that autumn, Humphrey would have won.

Similarly, of course, we now have the Democrats uniting with some enthusiasm around Biden’s vice president, the former California Sen. Kamala Harris, who for now at least is polling close to the Republican nominee, former President Donald Trump.

Political impact, immediate and long term

The response to LBJ’s announcement in 1968 came in waves of events and attitudinal change. The first reaction was amazement mixed with approval, a recognition that this consummately ambitious politician had made the ultimate sacrifice.

Within days there were polls showing LBJ’s approval soaring back up above 50%. Messages of approval came from everywhere, and there were tributes to his statesmanship in the media – even from longtime critics.

But the good feelings were short-lived. Within the week of LBJ’s announcement, Martin Luther King Jr. was assassinated in Memphis and many American cities were convulsed in rioting. RFK’s assassination came a month later, further deepening the sense of tragedy that hung over presidential politics that year.

Much of the coverage of the LBJ-Biden parallels will note that, beyond the historical parallels between LBJ and Biden, Monday’s commemoration is also a reminder to Democrats that the 1964 act was a turning point in more ways than one and a double-edged sword in political terms.

As LBJ himself was among the first to acknowledge, the 1964 act set in motion a realignment in U.S. politics that has shifted historical voting patterns and radically altered the dynamics within both major parties. Those changes have been central to U.S. election strategies and outcomes for the last six decades and continue to reverberate today.

Historians recount how LBJ himself foresaw what was to come. After signing the bill into law, he reportedly turned to a confidant and said he feared Democrats had “just lost the South for a generation.”

Whether LBJ himself said those words at that precise moment or not, the timeline of a generation was, if anything, too short. The South has become, and remains today, the stronghold of the Republican Party in much the way it was for the Democrats for a century before 1964.

Most of the South today may well be less hospitable for the Democratic Party of today than ever before. Even in the heyday of Richard Nixon’s “Southern strategy” or Ronald Reagan’s powerful appeal to the region, Democrats held a majority of Southern governorships and Southern seats in Congress (Senate and House). But that changed dramatically in 1994, ironically in the presidency of Arkansas Democrat Bill Clinton.

In that year’s midterm elections, Republicans for the first time won the majority of Southern governorships and Southern seats in the House and Senate. The GOP has continued to hold a majority of these offices ever since and is favored to do so in all three categories again in November. A few of the most populous Southern states: Texas, Florida, Georgia, North Carolina —have been competitive in recent presidential cycles. All but Texas have voted at least once for either Biden or President Obama. Georgia and North Carolina are still considered in play this November.

And all four of these states may well become more competitive again at the state and local level as the share of the vote cast by non-white citizens increases. Texans who speak a language other than English at home are already more than a third of the state’s total population, a proportion likely to grow given recent demographic trends.

But for now, the South remains the anchor for Republican success in the Electoral College and the main source of its strength on Capitol Hill. The Republican Speaker of the House is from Louisiana, the Republican leader in the Senate is from Kentucky. The Mountain West and the Plains States are generally just as Republican, but they have far fewer seats and accommodate at least a few Democrats from their more urban areas (Kansas City, Omaha, Denver, Albuquerque, Phoenix, Las Vegas and Salt Lake City).