Marco Rubio’s speech suspending his campaign after his crushing loss in the Florida primary was a requiem for an entire style of Republican politics.

Rubio represented an upbeat, opportunity-oriented vein in the GOP that ran through George W. Bush’s compassionate conservatism back to the late supply-sider Jack Kemp, who practically made a civic religion out of optimism and inclusivity.

Donald Trump has grabbed this Kempian tradition by the collar and frog-marched it from the room with all the delicacy of one of his security guards ejecting a troublesome protester from a rally.

Kemp, a former pro quarterback who was a congressman from Buffalo for years, was the chief proponent of the Reagan tax cuts. To read the recent biography of him by journalists Fred Barnes and Morton Kondracke, “Jack Kemp: The Bleeding-Heart Conservative Who Changed America,” is to be struck by Kemp’s touching naivete by the standards of the 2016 GOP race.

Kemp eschewed personal attacks and opposed negative campaigning. He believed “the purpose of politics is not to defeat your opponent as much as it is to provide superior leadership and better ideas.” And the central idea was, always and everywhere, tax cuts.

Kemp wanted the GOP to be a “natural home of African-Americans.” He favored openhandedness on immigration. He cared deeply about the plight of the urban poor, and about what he called — long before Jeb Bush — “the right to rise.”

In foreign policy, he was a friend of freedom and stalwart advocate of human rights.

Kemp influenced the debate and a generation of conservatives, but his own flaws as a highly undisciplined candidate and the monomania with which he hewed to his ideas limited him as a candidate at the national level.

But Kempism lived on in George W. Bush, whose compassionate conservatism was latitudinarian on immigration and sought to win over minorities by softening conservatism’s edges.

Bush’s foremost domestic achievement was an enormous tax cut, and his Freedom Agenda was a Kemp-like advocacy of human rights on steroids.

This year, Trump has crushed Bushism underfoot. Yes, Trump has his own large-scale tax cut, but it has been an afterthought compared with his themes of immigration restriction, protectionism and a robustly nationalistic Jacksonian foreign policy.

After destroying Jeb Bush, Trump turned his attention to Rubio, a candidate who was Kempian in tone and affect. “I ask,” a visibly exhausted Rubio said in his Florida speech, “the American people do not give in to the fear, do not give in to the frustration.” Actually, if the Trumpian plurality in the Republican electorate has anything to say about it, fear and frustration will be high on the nation’s agenda in the fall.

Trump’s iteration of the Republican Party won’t have a bleeding heart; it will be out for blood. Far from eschewing negative campaigning, personal abuse will be its calling card. It will care less about policy than attitude and shibboleths. Electorally, it will repel minorities and hope to run up the score with whites. It won’t have an open hand on immigration but will talk of mass deportation. It won’t care about human rights, and in fact will be happy to violate them — or threaten to — as the national interest and a desire for vengeance dictate.

The politics of Jack Kemp were inadequate in many ways — he was wrong on immigration and too obsessed with reliving the glory days of the Reagan tax cuts — and the party was due for a populist refurbishing. Yet Kemp represented a belief in the future and the power of ideas that was admirable, and at its best, invigorating.

Today, the most prominent representative of Kempism is the supply-sider’s former protege House Speaker Paul Ryan, an earnest policy wonk who has advocated Kempian ideas for years. At this moment, it looks like his reward may well be presiding over a Republican convention that crowns Trump as the party’s nominee and most important national voice.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.