On July 14, 1948, a young mayor and soon-to-be senator from Minnesota stood on the floor of the Democratic National Convention and challenged his party to commit itself to the cause of civil rights, "the issue of the 20th century."

Sixteen years after Hubert Humphrey's speech, President Lyndon Johnson signed the Civil Rights Act into law — and Humphrey himself was elected vice president of the United States.

But in the summer of 1967, a young senator from Minnesota — chosen to fill Humphrey's seat — invited a young navy lieutenant named Carlos Campbell to testify before the Senate Banking Committee's subcommittee on housing. After flying recon missions during the Cold War, Lt. Campbell had been assigned to the Pentagon. But when he and his wife looked for apartments in Arlington, Va., they found that vacancies kept disappearing as soon as landlords realized the Campbells were Black.

Housing discrimination had, in theory, been outlawed in the Civil Rights Act of 1964. But the provision didn't cover privately owned housing, and in any case it was rarely enforced, leaving many cities effectively segregated. A generation of Black families were relegated to under-resourced neighborhoods, locked out of homeownership, denied access to good schools and jobs, and refused admittance to the growing middle class.

Most senators would have preferred not to talk about it. A lot of white Americans were uncomfortable with the idea of Black families moving into their neighborhoods, and the issue had become something of a political third rail.

But if there's one thing that defined Walter Mondale, it was his willingness to tell hard truths.

Of course, there wasn't just one thing that defined him. Fritz was funny, kind, endlessly generous with his time and wisdom. He loved his family, he loved his staff, and he loved to serve. He was always more interested in earning respect than commanding fear. He never forgot a birthday.

Still, for many, the indelible image of the man was the moment when he stood on the stage as the Democratic nominee for president and told America a hard truth that, it turned out, most voters didn't want to hear. "Mr. Reagan will raise taxes," he said, "and so will I. He won't tell you. I just did."

Mondale, the story goes, was simply too honest and honorable of a man to get elected president. But the truth is, Fritz proved that you could be both a decent human being and an accomplished politician — especially if you measured accomplishment not by the titles you held (although he held plenty) but by the progress you made.

Which brings me back to 1967, a time not terribly unlike ours, with a generation rising up to protest the brutality of racism in America. Leaders called for calm, but Fritz understood that the civil unrest disturbing so many American communities was rooted in something real — the systemic racism embedded in every aspect of our society. And he knew that as long as housing discrimination continued to distance Black America from white America both physically and economically, there would be — could be — no progress and no peace.

"We have to show that we intend to be decent Americans," he said at one of that summer's subcommittee hearings. "We must show that we don't intend to live separately in this country but that we intend to live together." So he teamed up with Republican Sen. Edward Brooke of Massachusetts to introduce the Fair Housing Act of 1968.

Segregationists complained that the bill was "robbing all Americans of their basic rights of private property," and — stop me if you've heard this one — used the filibuster to prevent it from moving forward. But Fritz persisted, patiently and thoughtfully, and the bill finally passed the Senate in April 1968, just hours before the murder of the Rev. Martin Luther King Jr.

Half a century later, Fritz observed that his landmark legislation has still not been fully implemented, defining the intervening decades as a time of "gradual progress and frequent setbacks." Minnesota remains one of the most residentially segregated states in America.

Indeed, it turns out that civil rights is also the issue of the 21st century. And maybe that's the hardest truth of all when it comes to this sacred cause: that this "good fight," as Fritz put it, will never truly be done.

But as a senator from Minnesota who sits on the same Senate Banking Committee where Mondale spearheaded the passage of the Fair Housing Act, I hope that his memory will be not just a blessing, but a reminder of his courage, his candor, and his simple human decency.

Tina Smith represents Minnesota in the U.S. Senate.