The unprecedented six-month delay in bringing Anatoli Scharansky to trial on espionage charges may signal Communist retreat from a semiblackmail policy of using the leading Soviet dissident to force President Carter to cool his human-rights campaign.

That is the conclusion of some Kremlinologists, in and out of the Carter administration. Last October, these analysts leaned strongly the other way: that Scharansky, a major figure among dissidents demanding Kremlin adherence to human-rights commitments made at the 1975 Helsinki conference, would be the victim of the first Soviet "show" trial since 1970.

But apparently the refusal of the Carter administration - notably Ambassador Arthur Goldberg, chief U.S. delegate to the Belgrade conference - to knuckle under persuaded Moscow to change its tune.

Instead of toning down his grim recitation of Soviet human-rights violations, Goldberg stepped it up - and then returned here last month to engender greater support from Carter.

Scharansky was arrested on unpublished charges of espionage for the United States - a charge categorically denied by Jimmy Carter. Soviet law requires bringing a suspect to trial within nine months of the charge. Experts here recall no case in which the defendant in a political (as opposed to a criminal) case has been given as long an extension as six months - and few noncriminal cases with any extension at all.

Proof does not exist as to the Kremlin's motives. It can be argued, for example, that the six-month postponement (announced Dec. 16) would bridge impending U.S.-Soviet developments: a new strategic-arms agreement, a Carter-Brezhnev summit and the end of the Belgrade conference. The Soviet game might be to delay a bloody trial of Scharansky until after that summit.

But most Kremlinologists take a different view: that in the face of repeated, ominous and unpublicized warnings from the President on down, the Kremlin may have concluded that the trial could have a devastating effect on relations - before or after a Carter-Brezhnev summit. If true, this means that the politicians, led by Brezhnev, hold more power in the Kremlin that the KGB (the Soviet police apparatus), a matter of great significance.

An unannounced tete-a-tete with Laurence A. Tisch, the Jewish leader and Manhattan millionaire who runs Loews Corporation (theaters, hotels, tobacco and insurance), has opened new political doors to New York's fatcat goldmine for Sen. Howard Baker (R-Tenn.), a prospective 1980 Republican presidential candidate.

At Tisch's request, he and the Republican Senate leader talked Mideast and economic politics in Baker's office for half an hour on Nov. 29. Their consensus: President Carter had fumbled Mideast peace and was making a mess of the economy. That combination has now brought Tisch, a 1976 Carter man, to Baker - ostensibly for Baker's 1978 Senate campaign but actually looking to 1980.

Tisch will wine and dine Baker with a select group of well-heeled friends in New York Jan. 17, following a fund-raiser given by Wall Street financier Bernard Lasker and other Republican Baker backers. Tisch's immense contributions to Israel (close to $1 million every year for the United Jewish Appeal) make him a major force in the American Jewish community.

Footnote: Another 1980 Republican hopeful, Sen. Bob Dole (R-Kan.), is also courting and being courted by American Jews, leading to the possibility of continuation of the shift of Jewish voters to Republican presidential tickets. The shift went from 18 per cent in 1968 to around 35 per cent in 1972 and 1976.