Donald Trump's comments and proposed policies about immigrants, jobs, and terrorism have not only raised fears among Latinos, Muslims, and many politicians and journalists, they've raised fears among Republicans—who came out of the 2012 election with a postmortem suggesting the party's future was at risk if it could not expand its reach outside of white voters.

But what really threatens to cost him the election is the African-American vote. Trump is polling so badly among blacks that it's not only unprecedented, it seems mathematically impossible: zero percent in the crucial states of Ohio and Pennsylvania in a mid-July Marist poll; one percent in a June Quinnipiac poll; four to 12 percent in a series of February polls. If Trump indeed got four percent of the black vote in November, that would be comparable to when John McCain ran against the man who would become the first black president.

A couple weeks ago, FiveThirtyEight's excellent political reporter, Clare Malone, did a thorough dive into how the GOP lost the votes of, well, every significantly large minority in the country, becoming a party of "breathtaking whiteness." And she starts somewhere very interesting:

In “Party Ideologies in America, 1828-1996,” political scientist John Gerring marks the beginning of the modern Republican Party as Herbert Hoover’s shifting campaign rhetoric in 1928 and 1932, when he talked more about the virtues of the American home and family than hard-tack economics. Hoover’s oratory about the progress of the individual being threatened by an overzealous government bureaucracy stuck around for the next eight decades, and the wisdom of generations has helped us discern that this was indeed the start of a new Republican era.

But it's missing something significant, something I learned when I interviewed Ethan Michaeli about his epic history The Defender: How the Legendary Black Newspaper Changed America. In his book, Michaeli weaves the Chicago Defender's work in and out of the country's evolution in the 20th century, from boxing rings to Chicago wards to the highest echelons of White House politics.

And this is how Chapter 10 begins:

In the final weeks of the 1928 General Election, The Defender printed a series of articles and editorials that listed postwar grievances with the Republican Party. In Washington D.C., where the federal government was in direct authority, Republican presidents Harding and Coolidge, as well as Republican majorities in the U.S. Congress, had not only acquiesced to the segregation of public transit, but failed to stop or even criticize parades by thousands of Ku Klux Klansmen before the White House. The newspaper was particularly dissatisfied with the current Republican nominee for president, Herbert Hoover, who had spoken favorably of making the party "lily white" and excluded African Americans from their traditional role in that year's Republican National Convention. Most troubling of all was the candidate's covert backing from the Ku Klux Klan, whose members despised the Democratic nominee, New York Governor Al Smith, because he was Catholic.

This was just 65 years after the Emancipation Proclamation was signed. Many people who had been emancipated from slavery by the actions of a Republican president were still alive, with many more living under the rule of Democratic, Jim Crow southern politicians. So what The Defender did next was quite bold:

Finally, in an October 20, 1928 editorial entitled "What We Want," The Defender made a dramatic announcement: "We want justice in America and we mean to get it. If 50 years of support to the Republican Party doesn't get us justice, then we must of necessity shift our allegiance to new quarters."

It was the first time The Defender had failed to endorse the Republican presidential candidate since 1912….

(In the run-up to the 1912 election, Woodrow Wilson, despite a typical history as a Southern Democrat, had reached out to black voters, including leaders like W.E.B. DuBois. After Wilson's victory, the paper reported that "a 'substantial' number of blacks supported him." Once in office, Wilson immediately alienated his black supporters.)

"Robert Abbott [founder of The Defender] is a diehard Republican his whole life," Michaeli told me. "But with Hoover, who is explicitly… I wouldn't describe him as a racist, but he's interested in what he called a 'lily white' Republican party. This is after generations in which the Republican Party has stood for racial justice, is founded on racial justice. So Abbott feels that it's quite a betrayal. At this point, even he is frustrated with the Republican Party. And there's that famous [Defender] cartoon. There was a phrase, 'the Republican Party is the ship, all else is the sea,' and there's a cartoon The Defender runs that says, 'If this is the ship, we'll take the sea.'"

The Defender did not immediately turn against the GOP as a whole. As Michaeli describes, the former alderman Oscar De Priest was running as a Republican for the U.S. House, and poised to be the first African-American in Congress from a Northern state. De Priest won and remained in office until 1935, a counterweight to the thawing relationship between The Defender and Democrats, which picked up after four years of Hoover:

The Republican National Convention was held in Chicago that summer, which, to those at The Defender, made the near-absence of African Americans all the more galling. So consistently had Hoover pursued his policy of making the party "lily white," that the newspaper had to fight even to get African American delegates seated.

By contrast, black delegates spoke at the DNC, one month later in Chicago, where The Defender received a comparatively warm reception from Franklin and Eleanor Roosevelt. In exchange, the paper framed the convention and its nominee in a positive light. Hoover met with a large black delegation at the White House, but "still refused to be photographed with the group… maintaining his policy of not appearing in print with African Americans."

"But they don't quite break with the Republican Party at that point," Michaeli says. "It really takes Abbott's nephew and successor John Sengstacke, and the Roosevelt administration—and specifically within the Roosevelt administration, Mary McLeod Bethune—as the forces that start to realign not just The Defender, but black leadership, and then the black masses behind the Democratic Party. It's a long campaign that really comes from leaders of that caliber and at that level. You couldn't have done it without Roosevelt, and without Mrs. Roosevelt as much as Franklin."

Bethune, the director of the Office of Minority Affairs in the National Youth Administration and a conduit between the cabinet and black leaders, was a friend of Eleanor Roosevelt, who pushed her husband to employ Bethune in his administration.

The Defender's leadership had correctly perceived something about Roosevelt. But it wasn't enough to endorse him, given the still quite racist nature of the Democratic Party as a whole. But the tipping point was near. De Priest ran against Roosevelt's New Deal as "socialism and radicalism" (depends on your point of view, I guess) and because it perpetuated segregation (he had a point there). And he lost his 1934 election to Arthur Mitchell. Mitchell—who had switched parties just two years earlier—became the first black Democrat in Congress. "From all indications not only in Illinois but all over the country, black voters across the nation have taken President Franklin Delano Roosevelt at his word, that the New Deal is not to be circumscribed by races, colors, or deeds," wrote Defender reporter Archie Fields.

Roosevelt's word did not necessarily hold. As Ira Katznelson has documented, segregation persisted through government programs and employment during the New Deal, World War II, and its aftermath, and "contends that those programs not only discriminated against blacks, but actually contributed to widening the gap between white and black Americans—judged in terms of educational achievement, quality of jobs and housing, and attainment of higher income." The Defender's editorial board was prescient in 1932, when it found reason to praise Roosevelt but distrust the Democratic party as a whole.

But Hoover had also done tremendous damage to the Republican Party among a constituency that owed more to it than, perhaps, any constituency had owed a political party in the country's history. Thanks to the strength of that relationship and the power of party politics, the party would continue to retain black voters for decades after the Hoover administration, but it slipped away, generation after generation.

On the other side, the Democratic Party's intransigence in supporting black voters alienated from the GOP lengthened the process. Michaeli described the Kennedy campaign's relationship to black voters to me as "diffident," and outlined how a brilliant former Defender reporter turned political operative, Louis Martin, was able to make a late push among black voters that pushed John F. Kennedy over the top. In fact, Michaeli lays out a compelling argument that Martin's machinations were effective enough to sell The Defender on Kennedy, and its endorsement pushed Kennedy ahead by 190,000 votes in Chicago's black wards, in a state he won by fewer than 10,000 votes. The politics of Lyndon Johnson and Richard Nixon would complete a process that had begun decades before.

It was not the end of the Party of Lincoln as a big tent, but the GOP lost the diverse Muslim vote much faster. Once holding a majority among the growing religious minority that ranged from decent to dramatic as late as 2000, their support among that demographic is now comparable to their support among African-Americans, which pollster John Zogby called "virtually unprecedented."

Latinos have heavily favored Democratic presidential candidates every election since 1980, but George W. Bush made substantial inroads, following Bob Dole's 21 percent vote among Latino voters with 35 percent in 2000 and a high of 40 percent in 2004. By 2012 it was down to 27 percent for Mitt Romney. Recent polls suggest that Donald Trump could cut that already low number in half. In 2016, 88 years after The Defender's Robert Abbott raised the first warning, a party once synonymous with racial justice could find that legacy has reached its logical, even mathematical, end.