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As Hubert Humphrey, the 37-year-old mayor of Minneapolis, led the Minnesota delegation to the 1948 Democratic National Convention in Philadelphia, his primary goal was to help persuade the Democratic Party to adopt a strong civil rights position. The party's leadership argued that doing so would threaten party unity in a critical election year. President Harry Truman, who had succeeded to the presidency upon Franklin Roosevelt's death in 1945, was a clear underdog in his bid for election in his own right that fall.

Party leaders were content to recycle the 1944 civil rights platform plank because they didn't want to alienate Southerners; they warned Humphrey that he would divide the party and jeopardize his own career.

But Humphrey argued that Truman himself had made civil rights the central issue by creating a presidential civil rights commission which recommended broad legislation. He urged the platform committee to embrace Truman's already solid record on civil rights. After heated debate, the status quo majority plank carried decisively. Humphrey pledged to take his minority plank to the convention floor.

As Humphrey sat on the rostrum on July 14, 1948, 75 years ago, waiting to address the convention, the powerful party boss in the Bronx, Ed Flynn, leaned over and asked to see the speech. After reading it quickly, Flynn exclaimed, "You go ahead, young man. We should have done this a long time ago." He promised New York's votes and said he would try to get others.

As Humphrey stepped to the podium, the audience hushed. He spoke less than 10 minutes, but his voice was filled with passion: "… there are those who say to you — we are rushing this issue of civil rights. I say we are a 172 years late. … The time has come for the Democratic Party to get out of the shadow of states' rights and walk forthrightly into the bright sunshine of human rights."

"While I was saying all that," Humphrey later recalled, "my father was sitting right there in the hall. When so many people were trying to talk me out of it, he was the one who urged me on. … And how proud I was to hear my father's voice announce the eight votes of South Dakota in favor of my amendment. Our plank carried by sixty-nine votes, and it was a big, big day for us."

The auditorium exploded with applause — delegates paraded into the aisles waving state standards. Southerners remained seated. A nervous Sam Rayburn of Texas, the convention's chairman, feared that events were getting out of hand and could prompt a "walkout" of Southern delegates, weakening Truman's already slim chances in November. Rayburn failed to stall a vote; when it came the liberals had won handily. After a two-hour recess, 35 Southern delegates marched out of the auditorium and into a rainstorm.

Truman and his advisers had watched the proceedings on a small White House television, becoming angrier as they saw their worst fears realized. Truman biographer David McCullough captured the moment: "… Truman spoke of Humphrey and his followers as 'crackpots' who hoped the South would bolt. But the fact was the convention that seemed so pathetically bogged down in its own gloom had now suddenly, dramatically pushed through the first unequivocal civil rights plank in the party's history; and whether Truman and his people appreciated it or not, Hubert Humphrey had done more to reelect Truman than anyone at the convention other than Truman himself."

In November, Truman was indeed unexpectedly re-elected president, and Humphrey became the first Democratic senator in Minnesota history. In the Senate he resumed his civil rights campaign, culminating in 1964 when he became the Senate floor manager of the Kennedy/Johnson "public accommodations" bill.

Humphrey threw himself into organizing a floor fight to overcome a filibuster by Southern Democrats and conservative Republicans. The key to success was winning the support of Sen. Everett Dirksen of Illinois, the Republican leader, who had 22 amendments and with whom Humphrey met daily to explore possible compromises that would allow Dirksen to make his dramatic move.

He finally did so on June 9, 1964. Humphrey called for a cloture vote the next day that ended the filibuster by a stunning vote of 71 to 29. Dirksen had brought 11 additional Republican senators with him to embrace the most significant civil rights bill in American history.

Later that year President Lyndon Johnson selected Humphrey as his running mate. Once elected vice president, Humphrey became the White House point person and played yet another critical role in passing the historic Voting Rights Act of 1965, again with bipartisan support.

There can be little doubt that these two monumental civil rights bills could not have passed without the huge impetus of Humphrey's 1948 speech, which gave activists in the growing civil rights movement confidence that they were not alone. There followed an all-too-brief moment when it appeared there might be a coming-together of the parties on this profound issue. Sadly, it passed, and the country gradually slid into the politically polarized condition where hard-right extremists have been allowed to eviscerate — whether in the courts, the Congress or state legislatures — some of the most fundamental rights that Americans enjoy.

Now, 75 years after Humphrey delivered one of the most consequential speeches in American political history, we should reflect on this pivotal moment that enabled the United States to take a huge step toward equal justice and equal opportunity. Today Oxford University Press is publishing, in the tradition of its prestigious Pivotal Moments in American History series, a new book titled "Into the Bright Sunshine" by journalist Sam Freedman that promises to be the definitive account of Humphrey's speech.

May it remind us of what courage, principle and perseverance looked like in 1948 — and what will be required to find our own pivotal moments to put the U.S. back on course.

Richard Moe was chair of the Minnesota DFL Party, 1969-1972, and chief of staff to Vice President Walter Mondale/assistant to President Jimmy Carter, 1977-81.