Shortly after Rep. Jack Kemp guided through the platform committee a foreign policy/defense plank free of embarrassing rightwing amendments, he was called aside by a senior Reagan aide for congratulations and advice.

The congratulations: his work on the platform had erased the image of Kemp as a "Jacky One-Note" obsessed with tax reduction. In fact, said the aide, the performance had greatly enhanced his own opinion of Kemp.

The advice: steep yourself in the platform planks with which you are least familiar -- agriculture health, transportation. Talk about them, not taxes.

That conversation showed that Kemp, given up for dead as a vice presidential prospect a month ago, was back again -- though certainly not at the top of the list. He had not only intellectually dominated the platform proceedings, but had finally demolished the old canard of the lightweight football player high on cheerleading and low on brain matter. "I'll tell you frankly," Frederick Biebel, Connecticut's veteran Republcan national committeeman and a top Reagan operative, told a friend, "that Jack Kemp went up 300 percent in my estimate this week."

Several Reagan insiders have conclu-ded that if Ronald Reagan wants a dynamic campaigner to woo the blue-collar voter, he cannot do better than Kemp. Reagan aides have complained in recent weeks that the aggressive congressman from Buffalo is a chronic complainer whose skin is too thin for big-time politics; many were won over last week.

Kemp's irremediable failing is that he does not and cannot reassure the party's moderate wing, still uncomfortable with Reagan. George Bush's ability to do just that keeps him in the vice presidential picture, despite sour thoughts about him by Ron and , more particularly Nancy Reagan.

But that has led one senior adviser to propose a serious -- and public -- bid to Gerald R. Ford, who probably cost himself reelection by not making such an offer to Reagan in 1976. Despite constitutional complications caused by the fact that Reagan and Ford now both vote in California, the adviser considers such an offer a no-lose proposition.

If Ford says yes, the Republicans have a Reagan-Ford ticket that everybody agrees would be the strongest possible. If Ford says no (which likely would be the case), Reagan would have done his duty to the moderates and would not be obligated to take on Bush.

Even so, there would be pressure to pick a running mate offensive to nobody -- specifically, sen. Richard Lugar of Indiana. But vibrations from the Reagan campaign have turned negative. One middle-level staffer contorts his mouth in an attempted mimicry of Lugar. A senior staffer called the Hoosier Rhodes scholar "a wimp," adding: "Can you imagine how it would look with him standing on the platform next to the governor [reagan]?" Seasoned professionals do not usually talk that way about the man they think their boss will pick.

Just such second looks at Lugar, as we reported a week ago, led Reagan's senior staff to seek new faces -- a search that turned up Gov. Albert Quie of Minnesota. When Quie's trial balloon attracted little favorable interest, the reappraisal of Kemp commenced.

While making converts by his platform committee performance, Kemp put his intellectual stamp on the platform as has no individual in memory. The most obvious example was endorsing the Kemp-Roth tax bill by name in its original dimensions: a 30 percent tax cut spread over three years.

The long effort by Dr. Alan Greenspan, President Ford's chief economic adviser and now a Reagan adviser, to make it "three years or more" died in Detroit.

More impressive was Kemp's success (collaborating with his tax-cutting colleague, Sen. William Roth of Delaware) in amending the platform to call for "a monetary standard." That came closer to Kemp's goal of a revived gold standard than Kemp dreamed possible or that traditionalist Reagan advisers such as Dr. Milton Friedman thought prudent.

Kemp successfully kept labor-baiting out of the platform and fought off a barrage of rightwing amendments by Sen. Jesse Helms of North Carolina. He bought off a Helms protectionist amendment on foreign trade in return for a mealy-mouthed compromise and then talked Helms out of introducing a double-barreled amendment to revive the Panama Canal issue and attack the Trilateral Commission.

This was a remarkable performance for the former professional football player whose personality and philosophy made no mark whatever on the 1976 convention. Chances for this being rewarded with the vice presidency depend on whether Reagan is in a mood for risk-taking.