YOU KNEW IT was only a matter of time before medium cool would take over all the election campaigns in the world -- and now, sure enough, comes a report by staff writer William Claiborne, direct from the political-party boiler rooms of Israel: two of the top names in the American candidate-packaging business turned up in that country for the Making of a Prime Minister, '81.

Straight out of the Annals of Strange International Bedfellows came these curious pairings: to groom incumbent Menachem Begin there was New York-based consultant david garth, whose past customers have included presidential candidate John Anderson, New York Mayor Ed Koch and Los Angeles Mayor Tom Bradley; and to help manage opposition candidate Shimon Peres was David Sawyer, backfield coach for Sen. Edward Kennedy and a string of candidates for governor.

For this particular contest, both advisers were apparently quick to sense the importance of going after the Jewish vote; and each characterized his candidate as cool-headed and in command. We noted also that both contenders knew better than to concede too early, because that can prove costly to fellow candidates when the polls are closing later on the West Bank.

This is not the first time that Messrs. Garth and Sawyer have sold their marketing skills to overseas campaigns, either. The two faced each other in -- yes -- Venezuela; Mr. Garth has worked Bermuda; and Mr. Sawyer has been a coach in Costa Rica and the Dominican Republic. And just think what they or other American image-makers might have been able to do for other places: clearly Mr. Bani-Sadr could have benefited from a little exit-polling.

Should Yasser Arafat go to pin stripes for maximum credibility in the eastern states? If Mrs. Thatcher wears a basic black dress, will voters associate it with Ayatollah Khomeini? Should the ayatollah promise to nominate an all-female firing squad if re-elected?

Surely all this exporting of American media-polsavvy can do great things for the balance of trade. We're not sure what it will do for mental balance, worldwide.