Look into the closets and back drawers of the Republicans supporting Phil Gramm, Dan Quayle or Lamar Alexander for president in 1996 and you’ll almost certainly find a “Jack Kemp for President” button. What enthusiasm that man once excited among conservatives! Everything they had wished the dreary old GOP of Gerald Ford and Bob Michel to be, he was—dynamic, charming, unashamedly pro-market, unquestionably big-hearted. When he walked into a room, he lit it up.

He transcended the party’s internal divisions and contradictions. He was pro-life and pro-Israel, pro-gold standard and pro-Social Security, anticommunist and antiapartheid. He was “Yitzhak Kemp,” an “AFL-CIO conservative,” a “progressive conservative,” an “Abraham Lincoln conservative.” Seldom has a politician breathed more certainty that all Americans shared a common interest, that the hard money and low taxes that sent the Dow Jones average soaring would also enrich hardware store owners, beauticians and oil refinery workers.

It was Mr. Kemp who sponsored and championed the most important single piece of conservative domestic legislation of the 1970s, the Kemp-Roth cut in marginal tax rates. It was Mr. Kemp who argued most passionately for locating the 1980 Republican convention in Detroit, to underscore the party’s determination to win blue-collar and black votes. And at that convention, eager conservatives festooned themselves with “Reagan/Kemp” stickers, hoping against hope that Ronald Reagan would select the dynamic young congressman from Buffalo—not the colorless preppy from Greenwich—to fill the vice presidential slot, and (in the fullness of time) inherit the Oval Office.

It all seems quite incredible now.

Monday, after months of bad news from former supporters and contributors, Mr. Kemp announced his withdrawal from the 1996 race, and thus, at least for now, from active politics. What went wrong?

The simplest answer is Mr. Kemp himself—his repeated refusal to take the risk of running for higher office, his loquacity, his unwillingness to learn from experience. It’s easy to tick off his political misjudgments, culminating in the worst of them all—the failure to resign from the Bush cabinet in the summer of 1990 over the breaking of the “no new taxes” pledge and to run for governor of New York against a vulnerable Mario Cuomo. A Gov. Kemp who remained faithful to his tax-cutting principles after George Bush betrayed them—he could have burbled as loquaciously as he liked and still have been unbeatable in 1996.

But Mr. Kemp’s rivals suffer their share of personality faults too. Why were Mr. Kemp’s fatal when theirs were not?

Mr. Kemp seemed to pride himself on refusing to change with the times. The speeches he gives today can barely be distinguished from those he gave 17 years ago. Mr. Kemp is a political Dorian Grey, a man untouched by time even as everything around him is transformed by it.

As social order collapsed in the inner cities, Mr. Kemp kept promoting the same two pet nostrums that he imported from Margaret Thatcher’s Britain in the late 1970s, tenant ownership of public housing and enterprise zones, despite accumulating evidence that they will not work.

Enterprise zones have not yet had an opportunity to fail in America, although they have been tested and found wanting across the Atlantic. But as secretary of housing and urban development under President Bush, Mr. Kemp had a chance to try his tenant ownership idea. The cost was huge—in just four years, Mr. Kemp upped his department’s budget by 50%, from $19 billion to $27 billion—and the results were meager. Tenant ownership mutated almost instantly into yet another hideous bureaucracy under yet another deceptive acronym: HOPE, or Home Ownership for People Everywhere.

The privatization of public housing made Tories out of a wide swath of the British working class. But only 2% of Americans live in public housing, and they are overwhelmingly drawn from the ranks of welfare recipients, not workers. They are much less likely than their British counterparts to possess the cash to buy their homes (even at concessionary prices) and the skills to maintain them. Since American projects are vastly more violent, unattractive and deteriorated places than the British, and since superior private-sector housing is available relatively cheaply, those tenants who do amass a bit of cash are going to want to leave, not buy.

Mr. Kemp’s effort to apply the noncomparable British experience in the U.S. led to one of the strangest episodes in the history of the American welfare state, the Kenilworth-Parkside HOPE demonstration project. Mr. Kemp spent an average of $125,000 per apartment to renovate Kenilworth-Parkside. He then “sold” the units to the tenants on conditions that required them to put no money down and that precluded them from reselling their apartments on the open market, so as to prevent profiteering. To get HOPE through Congress, Mr. Kemp even had to promise to build one new unit of public housing for every unit sold.

In other words, HOPE—the very program that was supposed to replace state ownership of housing—ended up multiplying and entrenching it. Mr. Kemp had become so infatuated with tenant ownership that he traded away its substance to preserve the slogan.

This was more than mere obstinacy. Mr. Kemp believed, believed passionately, that the urban black poor were people pretty much like other Americans. If they seemed sunk in dependency and self-destructive behavior, the blame ought not to attach to some “culture of poverty” or to the bell curve—but to the perverse incentives of the welfare state. Yet Mr. Kemp until the very last weeks of his presidential hopes refused to come out for what he condemned as “punitive” Charles Murray-style reforms of that welfare state. The only escape from the dilemma was to roll back the welfare state in a way that didn’t actually deprive any beneficiary of its benefits—in other words, HOPE.

Mr. Kemp never fully reckoned with the horror and fear that the destructive behavior of the urban underclass provoked in the American middle class—or in his party. Mr. Kemp’s conservatism envisaged a little tinkering with the mechanism of government that would ignite economic growth and liberate the dormant entrepreneurial energies of the poor. Conservatism, 1990s-style, takes a far grimmer and more pessimistic attitude, and Mr. Kemp’s happy-talk sounded increasingly anachronistic and naive.

For all the boldness of his language, for all his fondness for the word “revolution,” Mr. Kemp never completely broke with the orthodoxies of postwar American liberalism. In the early Reagan years he clashed with David Stockman over the need for sizable spending cuts, and he lambasted Paul Volcker for raising interest rates to squeeze out the Carter inflation. Mr. Kemp didn’t want to cut taxes in order to shrink the government—at least, he seldom said so. He wanted, he insisted, to cut taxes in order to support government. Kempism often sounded suspiciously like a deal with liberalism: If you put me in charge of the revenue side of the ledger, you can run the expenditure side as you please.

Up to a point, Mr. Kemp was right: The lowering of marginal income tax rates between 1981 and 1990 triggered a 50% increase in personal income tax collections. But not even the abundant revenues of the Reagan years could keep pace with the extravagant commitments made in the Johnson and Nixon years.

As they grappled with the deficits spawned by the escalating costs of federal social welfare programs, more and more conservatives began to wonder whether the stodgy old Republicans overshadowed by Mr. Kemp in the 1970s hadn’t been right—whether it wasn’t government spending, after all, that was the core problem of modern government. If so, opposition to Big Government would have to be reincorporated as the defining doctrine of modern conservatism—leaving very little place in the movement for expansive, expensive Jack Kemp.

If Mr. Kemp’s withdrawal from the presidential race signals a new determination among Republicans to cut the federal government down to size, then it is welcome. All the same, those of us who once wore his button on our lapels could not help feeling sad at Monday’s news. No other conservative leader is as untinctured by the small, the petty, the mean as Mr. Kemp. There was always something great and generous about the man. If his policies were credulous or misconceived, his determination that Republicans offer hope to the poor too was noble and right.

His most recent fight exemplified all that is best in the man. Mr. Kemp could have preserved a discreet silence over California’s Proposition 187, a law that (among other things) cuts off schooling to the children of illegal aliens. He could have concentrated his attention on his points of agreement with Californians unhappy about high levels of immigration to their state. He did neither. Mr. Kemp has championed immigration throughout his career, and he declined to change his mind at the end—even if it cost him his last hope of the presidency. Jointly with Bill Bennett (who had earlier inclined to favor 187), he defiantly published his opposition to the measure, and campaigned against it. At HUD, Mr. Kemp stubbornly refused to budge on tactics; that same stubbornness was a strength when he defended a point of principle. Mr. Kemp’s problem was that he often had trouble telling the difference.

Perhaps the future will remember Mr. Kemp only as we remember James G. Blaine, the most popular Republican of the 1880s, and yet a man who never quite made the historical cut. But it would be more just if Mr. Kemp carried out with him an appellation he well deserves, the same appellation Dean Acheson applied to Harry Truman—“the captain with the mighty heart.”