In 1986, 34 years after he had first been elected to the U.S. Senate from Arizona, Barry Goldwater, the hero of the conservative movement that made possible the eventual election of Ronald Reagan, retired.

As Sen. Goldwater cleaned out his Capitol Hill office, I was privileged to listen as he reminisced about the 1964 presidential contest that would never take place: “Jack Kennedy and I had agreed that if we ran against each other in ’64, we would travel on the same day to Denver or Detroit,” for example, to speak to the same crowd on the same subject, whether it be “education or Social Security.” Then, with his characteristic candor, Goldwater added: “(JFK) probably would have kicked my ass.” But their entirely different “campaign would have been good for the country.”

No Americans old enough to remember ever forgot where they were when they heard the news that the president had been shot and killed on that terrible Friday in Dallas. For Goldwater, already organizing for the upcoming campaign, the assassination and Lyndon B. Johnson’s succession to the Oval Office all but sealed his political fate. American voters, in a state of shock and sadness, were not of a mind to have three different presidents in the space of 14 months.

But Goldwater did run in 1964. He ran as an unapologetic conservative who was on record as being for giving NATO commanders authority to use nuclear weapons, withdrawing the U.S. diplomatic recognition of the Soviet Union, selling the Tennessee Valley Authority and making Social Security voluntary. During that memorable year, Goldwater was one of just six Senate Republicans who voted against the historic Civil Rights Act – which outlawed nationally racial segregation and discrimination, then legally sanctioned in the states of the old Confederacy. In the election that November, Goldwater won 87 percent of the vote in Mississippi – an astounding Republican breakthrough – but carried only Louisiana, South Carolina, Alabama, Georgia and his home state of Arizona while getting just 38 percent of the national vote.

After the Johnson landslide, which produced better than 2-1 Democratic majorities in the House and the Senate, the Republican Party was all but dead, reduced to an out-of-step, predominantly Southern white minority.

But the obituary was premature. The GOP, proving that there is life after death, came back from the Goldwater debacle, assisted by Democrats’ errors and the tragic U.S. war in Vietnam, to actually win five of the next six presidential elections. If Gerald Ford had not done the admirable – pardoning his predecessor, Richard Nixon, and thereby enabling an embittered nation to heal – Republicans could well have won the White House six times in a row.

But there was a severe cost to Republicans from 1964. President Dwight Eisenhower had won 4 in 10 African-American voters, but in the 13 elections since LBJ signed the 1964 Civil Rights Act, Republican presidential candidates have averaged just 10 percent of the black vote.

And that is the lesson from the Goldwater defeat that now-nervous Republicans must heed. President George W. Bush won 44 percent of the fast-growing Hispanic vote just three elections ago. As the GOP has become more immigrant-unfriendly, the share of Latinos backing Republicans has fallen. In 2008, John McCain received just 31 percent of the Latino vote, and for Mitt Romney in 2012, it was down to 27 percent. The real fear for Republicans is that just as 1964 became a watershed year for their party’s losing the African-American vote in perpetuity, presidential nominee Donald Trump could – by his language, his policies and his attitude – permanently reduce the GOP share of the Latino vote to 10 percent. That would be a killer.