In this season of revisiting the 1962 Cuban missile crisis, the emphasis is on fresh material indicating that President John F. Kennedy was ready to swap innocent old American missiles in Turkey for the new weapons Nikita Khrushchev was provocatively deploying in Cuba. He wanted not just to ensure that the crisis wound down without war but also to head off any charge that, ''when the blood starts to flow,'' he had failed to do what he could to avert it.

For this, the unreconstructed right pro-nounces Kennedy a wimp. For a considerably milder dalliance with this idea, you will recall, JFK's United Nations ambassador, Adlai Stevenson, was unfairly singled out and savaged by insider leaks at the time.

But what is most intriguing to me is the new material explaining how, given his readiness to deal in Turkey, Kennedy did not actually do so. How, in short, the Cuban missile crisis, already numbingly difficult and dangerous, did not take on the perilous additional dimension of a ''Turkish missile crisis'' as well.

Transcripts of JFK's ExComm (executive committee) on the climactic day of Saturday, Oct. 27, show a crucial role was played by Llewellyn E. Thompson Jr., a senior career diplomat who had just completed one of his two tours as ambassador in Moscow. He died in 1972.

Thompson, according to a new study by Raymond Garthoff, shared in the American consensus that the Soviet deployment was intended not to deter a U.S. invasion of Cuba -- none was planned, anyway -- but to redress Soviet strategic inferiority.

Nonetheless, Thompson knew Khrushchev was saying, publicly and privately, that the crisis stemmed from an American threat to Cuba. Remember: JFK had launched an ill-fated e'migre' invasion a year earlier, and the CIA and/or e'migre's were still making things hot for Fidel Castro.

So Thompson was ready when a grim president said: ''We're not going to get these {Soviet} weapons out of Cuba, probably, anyway. But I mean -- by negotiation -- we're going to have to take our weapons out of Turkey. . . .''

''I don't agree, Mr. President,'' said Thompson, ''I think there's still a chance that we can get this line going.'' He meant responding to Khrushchev's first letter of Oct. 26 suggesting a withdrawal of the new Soviet weapons in return for an American pledge not to invade Cuba, rather than responding to Khrushchev's second and more difficult letter of Oct. 27 demanding that American missiles in Turkey be thrown in too.

''He'll back down?'' asked Kennedy.

''Well, because he's already got this other {Cuban} proposal which he put forward,'' Thompson replied, adding: ''The important thing for Khrushchev, it seems to me, is to be able to say 'I saved Cuba, I stopped an invasion. . . .' ''

The president then went on, with Excomm knowledge and approval, to write back formally accepting the Cuba deal offered in the first Khrushchev letter. JFK also went on, without Excomm knowledge, to take out a bit of insurance, telling Khrushchev quietly that the missiles in Turkey were not up for swapping but would probably be removed (they were) in due course.

Whether the hint on Turkey figured in Kremlin calculations, we don't know. But we do know that the letter on Cuba brought an end to the crisis the next day, Sunday, Oct. 28. The offending missiles and jet bombers were soon removed and, though the conditions (verification, safeguards) binding the United States not to invade were never fulfilled, no invasion subsequently took place.

''I don't agree, Mr. President.'' Aides are supposed to give their best judgment. But this is the transcripts' only instance of an Excomm member's direct challenge to JFK. It came at a crucial moment and when the flow was going the other way, the wrong way, and it helped reverse that flow. It is electric evidence of a rare and wonderful poise, gutsiness and independence.

Tommy Thompson, the old Moscow pro, was only doing what he was hired for. Still, alone of Excomm members he spoke of the Soviets not as abstract any-country adversaries, the way the other members did, but as specific people whose ways he had known and words he had read. How fortunate were we -- and the Russians -- that he was there.