IN LATE MAY of 1964 -- just a few days before the California presidential primary showdown with Sen. Barry Goldwater -- Gov. Nelson Rockefeller's press bus was hopelessly lost on the streets of Los Angeles. The bus driver eventually spotted a police officer and stopped to ask him directions to a television station. Before the driver could speak, one of the reporter-comedians on board inquired: "Officer, could you direct us to the mainstream?"

That was a year and that was the campaign when Republicans like Henry Cabot Lodge, Williams Scranton, George Romney and Mr. Rockefeller were using works like mainstream, pragmatic, responsible and moderate to distinquish themselves from Sen. Goldwater, who was preseumably one of the above.

In fact, the Republican battle that year was more regional and generational than ideological. It was the East, particularly the Northeast, against the South and the west. Old money and established power against new money and new people. Brooks Brothers against La Coste. And it was a year in which eastern Republicans learned that nothing changes more quickly and more regularly in American politics than the phone numbers. For essentially the same people who had nominated Wendell Wilkie, Thomas Dewey and Dwight Eisenhower was given a harsh lesson in organization politics by thousands of committee amateurs under the banner of Barry Goldwater.

Twelve years later, at the Kansas City Convention, the progressive Republicans found themselves reduced in numbers and clout and fighting a rearguard action for Gerald Ford against Ronald Reagan.

Gerald Ford had always been a Grand Rapids conservative and never the prototypical eastern Republican either in style or outlook. But to listen to him extolled by Clifford Case, Elliot Richardson, Jacob Javits and Charles Percy, one would have concluded Mr. Ford was the direct lineal descendant of La Follette and Norris.

In 1980, with the lonesome exception of Congressman John Anderson, there is no Republican presidential candidate from the wing of the party that dominated its national conventions from 1940 to 1960.

Moderate Republicansim was always a little anemic in the matter of emotion. The 1964 rout of the Republican moderates was the complete triumph of passion over pragmatism. The Republican Party had turned away from the tepid liberalism of a earlier day, a fact recognized by Richard Nixon in 1968 when he wooed and won conservatives like Strom Thurmond and John Tower. Time and numbers were on the side of the non-eastern Republicans. Their ranks and states were and are still growing while population and power slipped from the eastern seaboard.

To listen to the Republican candidates -- Baker, Bush, Connally, Crane, ydole, Reagan -- is to hear a perfect choir, singing as one voice. On issues as diverse as national health insurance, the defense budget, Rhodesia policy, SALT, the need for tax cuts, and cutting the price and purview of government, the chief Republican challengers are in near-unanimous agreement. These Republicans seem to have achieved a rather unprecedented unity on national issues and, at the same time, to have recognized that the nonminating process if effectively dominated by conservative activists.

The remanants of the "responsible, forward-looking" Republican wing are threatening no walkouts. Instead, in many cases, in places like New York and Connecticut, these bloodied veterans are suing for peace and climbing on the Reagan train or maybe even supporting George Bush, who, at the very least, looks like a moderate. After all, the moderates always prided themselves on their pragmatism.