The distance between the former Republican leader and Donald Trump can be measured not only in degrees of ideology but in Kemp’s appeal to the nation’s better angels. PHOTOGRAPH BY MARK PETERSON / REDUX

When the House Speaker, Paul D. Ryan, the other day postponed, or rethought, any future endorsement of Donald J. Trump, the presumptive Republican Presidential nominee, he did it in the name of his party, an entity that Ryan, among others, seems to view as a fragile thing, to be regarded with brotherly affection, the very opposite of Trump’s view of the party as a sort of speed bump. The Republican Party, Ryan told CNN’s Jake Tapper, is “very special to a lot of us,” and he went on to identify it, and himself, as the home “of Lincoln, of Reagan, of Jack Kemp.”

That was a most revealing, and interesting, threesome, not only because Ryan left two admired Republican Presidents—Theodore Roosevelt and Dwight D. Eisenhower—off his list but because he included Kemp, a name still well remembered by fans of the Buffalo Bills, for whom he was a standout quarterback, though perhaps less so beyond the inner sanctums of think tanks like the right-of-center American Enterprise Institute and the Heritage Foundation, which lists to the right of the A.E.I. It made sense, though, for Ryan to invoke the name of a man whom he regarded as a mentor and who once considered Ryan a protégé.

Kemp, who died in 2009, served in Congress for eighteen years (from 1971 to 1989), representing a swatch of western New York near Buffalo, and became a passionate advocate of supply-side economics, the belief that tax cuts are pretty much a guaranteed spur to general prosperity. Kemp became a hero to the Reagan branch of the party and, in 1988, the year that George H. W. Bush won the White House, made a faltering attempt to run for President. He might have done better had he had the prominence of, for example, a New York Senate seat, which he’d contemplated seeking in 1980, but that would have meant challenging Jacob Javits, the incumbent Republican, who was suffering from Lou Gehrig’s disease. Kemp didn’t have the stomach for that; decency was his undoing. (A Nassau County supervisor, Alfonse D’Amato, defeated Javits in the primary, and, in a three-person contest, went on to win the first of three Senate terms.) The senior Bush appointed Kemp the Secretary of Housing and Urban Development and, in the 1996 Presidential race, he was Senator Bob Dole’s Vice-Presidential choice in what proved to be a hopeless match against Bill Clinton.

I got to know Congressman Kemp in the early nineteen-eighties, when I worked for a Buffalo newspaper. I was struck by his good spirits and his almost touching enthusiasm for the ideas he was exploring and expounding, such as a belief that the United States should return to the gold standard. One late fall day, we met for lunch on Capitol Hill and, after he explained why gold reserves should again be linked to the dollar, I asked him why the dollar had to be backed by gold. Couldn’t it just as well be tied to pork bellies? Rather than being annoyed that I was teasing him, Kemp grinned happily, leaned across the table, and said, “If you can see that, you’re almost there!”

Kemp was a cheerful, generous man, but what most deserves recognition, in what’s left of the Republican Party, is less his fascination with such byways as the “Laffer Curve” (the economist Arthur Laffer’s view of the relationship between taxes and revenue) and more his persistent voice on behalf of lifting up the needy, the jobless, the disenfranchised—take your pick among the shorthand expressions used to describe America’s poor. His commitment to bettering the lives of African-Americans was passionate and genuine. The Times’ Jason DeParle has written about how, during a frustrating time at HUD, Kemp kept urging the Bush Administration, and the budget police, to support, among other things, a plan called HOPE—the acronym for Homeownership and Opportunity for People Everywhere—with the aim of letting public-housing tenants own their apartments. In post-Reagan Washington, such causes won few allies. As Timothy Noah has pointed out, the man who uncritically signed on to some dubious economic theories was also someone who “conveyed a concern for America’s dispossessed that was unusually heartfelt, especially for a Republican”—which, given Ryan’s austere domestic priorities, makes his enthusiasm for Kemp both interesting and, often enough, confounding.

Ryan, for his part, acknowledged to Tapper that “we don’t always nominate a Lincoln and a Reagan every four years, but we hope that our nominee aspires to be Lincoln- and Reagan-esque”—and, presumably, Kemp-esque. Talk about aspiration! The distance between Jack Kemp and Donald Trump, or between Kemp and the preening Texas Senator Ted Cruz and the rest of this year’s Republican crop, is a distance to be measured not only in degrees of ideology, and gloomy anti-science ignorance, but in the appeal (speaking of Lincoln) to the nation’s better angels. In this long season, that seems as distant as Jack Kemp’s stubborn inclination to do the decent thing.