In the shifting world of California politics, there is no such thing as a self-perpetuating political machine. But the 190 attorneys who fill the wood-paneled and glass-walled offices of O'Melveny & Myers may be the next closest thing.

Partner Warren Christopher, under secretary of state-designate in the Carter administration, has helped build the reputation of O'Melveny & Myers as a politically influential corporate firm.

Christopher has been active in Democratic party politics, especially as the political mentor of former Sen. John Tunney. Other partners have helped all variety of politicians, including Ronald Reagan, Lyndon B. Johnson, Gov. Edmund G. Brown (both Sr. and Jr.), California Attorney General Evelle Younger and many more.

"They play both sides of the street and bar association politics as well, better than almost anyone else," according to Joseph Cerrell, a longtime political consultant to Democrats here. "I've seen campaign checks come in from clients of theirs," Cerrell said of O'Melveny lawyers. "There's an attorney's card clipped right to the check just so you won't forget who is producing."

O'Melveny & Myers is the biggest law firm in Los Angeles, known for its conservatism and the high quality of its work. The firm does not publish a client's list in the standard legal directories, but a reference book called Walker's Manual shows that its lawyers have represented IBM, Northrup, Technicolor, General Motors, Great Western Financial and Copley Newspapers.

Former members of the firm say past or present clients include Lockheed, the Los Angeles Dodgers, television producer Norman Lear, the late Gary Cooper, Occidental Petroleum and numerous banks and insurance companies.

In addition to its offices here, the firm has an office in Paris and a new one in Washington, opened last February.

"We do no lobbying at all," said James Green, chairman of the firm's management committee, in a recent interview. Nor, said Green, is the firm involved in much contract work with the Defense Department, because most of its clients have in-house lawyers for that kind of business.

O & M has tripled in size since 1961, insiders here attribute part of that growth to "political connections," as one put it. Green denied this. "We've had representation on both political sides in prominent positions," he said, "but these are individual decisions, not ones made by the firm."