George Bush pulled in one of the largest crowds of the still-young campaign here today, as nearly 1,000 members of the city's prestigious Commonwealth Club assembled to hear him attack the Carter administration.

Yet among the scores of tables in the Grand Ballroom of the St. Francis Hotel there were very few blacks, very few Hispanics, very few Chinese and very few people who did not seem well-to-do.

In San Francisco, just as in Pittsburgh and Cincinnati, in St. Petersburg and in Denver, Bush was speaking to people much like himself -- successful, business-oriented, comfortable and conservative.

Thus far in this campaign, Bush, by chance or design, has served as the Republicans' ambassador to the affluent.

Not that he plays this role exclusively. On Sunday, the vice presidential nominee traveled to Harlem to help dedicate a low-income housing project along with jazz musician Lionel Hampton, an old family friend who once campaigned for Bush's father, former U.S. senator Prescott Bush. w

On Wednesday, he visited a hog farm and had a bag lunch with factory workers at a heavy machinery plant in central Iowa. And late last week he spent time at a Veterans of Foreign Wars picnic and a dance in largely Mexican-American sections of San Antonio, courting a voting group whose good favor is essential to a Republican victory in the key state of Texas.

But for the most part, Bush has been taking the Republicans' message to those places where it is most likely to be embraced. His major speeches have been before a Rotary Club in Cincinnati, the World Affairs Council in Pittsburgh, the Tiger Bay Club in St. Petersburg and the Commonwealth Club here.

These groups, though mostly nonpartisan, all present a homogenized view of the American success ethic -- all their members have already made it.

In part, these appearances and the frequent stops at local fund-raisers for congressional candidates are part of the necessary spadework that comes at the beginning of national campaigns, said Bush press secretary Peter Teeley.

"For one thing his appeal to those (middle class) audiences is strong . . . but we are obviously not going to restrict Bush to Republican or upper-income groups entirely for the remainder of the campaign," Teeley said.

For some party pros, this early campaign pattern is hardly surprising. The people in Bush's audiences so far are the heart and soul of the Republicans' traditional constituency, and Bush handles them very well.

"I am optimistic about America," he tells them, and they respond with applause, just as they do to his mixture of self-effacing comments and hard-nosed sarcastic attacks on the Democrats.

When the presidential debates became a consistent subject of questions, for instance, Bush started telling his audiences that his running mate, Ronald Reagan, is "a fine debater -- and I can attest to that" -- a selfdeprecatory reminder of his failures in primary contests with the former California governor.

And today, at the Commonwealth Club meeting, Bush answered a question about his prospective role as vice president by saying, "What I must do is earn the confidence and respect -- through performance and knowledge -- of the president of the United States.

"If I do that, I'll have a lot to do. And if I don't, understandably, I will be the equivalent of unemployed."

His remark brought an immediate burst of laughter and applause. Near the back of the room, one man with distinguished silver-gray hair and an equally distinguished gray suit nodded happily to almost everything the candidate had to say.

"Right now we can get out to some states and show the flag" to such Republican supporters as that, Teeley said. "This will change as we get further into the campaign and put more emphasis on the major industrial states."

But for the moment, Bush is spending his time spreading the Republican credo of excessive government interference and excessive government failure to those who already believe.