Postwar politics has been enriched by two careers which fell short of winning the final prize. One was Hubert Humphrey's. The other was Robert A. Taft's. Both men died of cancer soon after their last quest for the presidency. Taft died 30 years ago this week. It is arguable that if Taft had never run, Ronald Reagan would never have won.

When Taft died on July 31, 1953, his body was placed in the Capitol rotunda, where his father's body had rested 23 years earlier. The father (president and chief justice) had embodied the Republican Party in 1912. The son helped keep conservatism intellectually reputable during its wilderness years, 1932-1952. And he advanced the process of getting conservatives to come to terms with the modern state.

Taft won his Senate seat in 1938, the year FDR's court- packing plan was an issue, the year Congress acquired a moderately conservative majority (Republicans and southern Democrats). That majority lasted until the 1964 landslide, when the Republican right at last got the nominee of its choice.

Although Taft was nearly 50 when drawn into national politics, and although he was drawn by disapproval of the New Deal, he helped conservatism outgrow the recriminatory tone of voice it acquired when defining itself in reaction against Roosevelt. He could be mistaken (as in opposing TVA), but was selective in opposing governmental activism. He favored the Reconstruction Finance Corporation, subsidized loans for farmers and homeowners and accelerated public works spending.

In three areas--education, health and housing--Taft was, some conservatives thought, unsound, because he favored federal programs. The programs were modest by today's standards, but his principle was, for his party, momentous. It was that the severe individualism of pure laissez-faire is an insupportable public philosophy because it is contrary to humane instincts and prevents the national government from dealing with matters important to the national welfare.

A negative tone has served Republicans (and Democrats) well when out of office. In 1946 the Republican slogan "Had Enough?" helped produce gains of 56 House and 13 Senate seats. Twenty years later, a Republican rookie won California's governorship using the slogan in Spanish--"Ya Basta!" (literally, "Enough already"). But Taft was a bridging figure, reaching out from negativism to a conservatism compatible with the government Roosevelt built.

In "Profiles in Courage," John F. Kennedy recalled the bitter criticism Taft received for opposing the Nuremberg trials. Taft thought the trials imposed ex post facto laws, punishing crimes not defined at the time they were committed. He was right that the trials used judicial forms for political ends, and were acts of vengeance. His complaint was brave, but too coldly lawyer-like. He was blind to the need to civilize vengeance and build a record of the crimes that called for vengeance.

Like Humphrey, Taft suffered from some of life's close calls. Had he been nominated either in 1948 or 1952, he might well have won. But what made him admirable--a willingness to lean into the wind--limited his appeal. And just as Humphrey at times seemed to be a caricature of liberalism--too bubbly to be serious--Taft sometimes seemed to be a cartoon of conservatism, earnest to a fault and an enemy of fun. No one was less suited than Taft to run against Dwight Eisenhower's smile.

It is now clear that Eisenhower was underestimated as a politician and president. But as a party leader he was at best indifferent. After the 1958 elections there were fewer Republican senators and congressmen than after the 1948 elections. Taft knew something Ike did not know or at least care about: party vigor depends on a sense of distinctive purpose, and hence on some clear doctrine. In that sense, Taft's torch has come through many hands to Reagan's hands.

In 1957 the Senate (acting, perhaps, on the dubious principle that is is as important as baseball) elected five former members to a "hall of fame"; Calhoun, Webster, Clay, La Follette and Taft. As Joseph Alsop wrote when Taft died, not since the era of Clay and Webster had politics been so influenced by someone who did not have the White House at his disposal.

Among Washington monuments, the memorial to Taft --a carillon on the slope of Capitol Hill--is modest. But his other monument is at the top of the Hill. It is a Republican Party more adapted to the age than it would have been if he had never left Cincinnati.