A PRESIDENT'S power to appoint -- or at least nominate -- others to office is one of his most influential means of governing. That power is wide in scope, pervasive in effect and exclusively a president's. He picks his vice president, Cabinet and personal staff, plus judges, regulators and a host of others. His choices define his taste and style in governing, and determine in large measure whether he actually advances the purposes and values for which he sought the White House in the first place. True, both his influence and policy direction are drastically reduced when a president simply names someone to, say, a Cabinet post and walks away, leaving an autonomous appointee. It is in the use a chief executive makes of his appointees, the guidance (and example) he offers, the counsel he takes back, the sense of common enterprise he imparts, that he makes his mark. But it all starts with the people.

Incontestably, the most important choice is that of the vice president, and here President Carter and Gov. Reagan have gone well beyond the formalities of ticket-balancing. Walter Mondale, a proven performer who has not languished in his post, and George Bush, an experience generalist, have different qualities and appeals, but both, rather unlike their chiefs, take naturally to politics, and you can see either of them as president.

Some of those aides from the governorship years that Mr. Carter brought to Washington have deservedly not fared so well in the public's esteem. There does seem a certain insularity that Mr. Carter has not altogether outgrown. Nonetheless, he has reached out to the large corps of able and sometimes distinguished Democrats who relish government service. That the whole of his administration is not greater -- quite the contrary -- than the sum of its Cabinet parts is due chiefly to his own strange method of governing. Mr. Reagan, with a couple of controversial exceptions, has included in his own campaign and, potentially, in his staff and Cabinet retinue creditable close associates from the Sacramento years. His California experience, and his campaign, have suggested a general readiness to apply the merit standard and to mix in pragmatic people with the sort identifiable with his own conservtive ideology.

The prospect of several Supreme Court openings and the court's central role have drawn special attention to the two candidates' approaches to the judiciary. Gov. Reagan has been disconcerting explicit in indicating a partiality for justices sympathetic to his judicial philosophy. Perhaps the best that can be said here is that every president favors like-minded justices but, happily, justices tend to be notoriously independent-minded. Mr. Carter's court nominees would likely be much more satisfactory to citizens with a strong liberal bent, and especially those who greatly admired the work of the Warren Court as distinct from its present successor. Mr. Reagan has made an unseemly promise in the matter of naming a woman to the high court. Meanwhile, Mr. Carter has already filled a record number of lower federal judgeships, most of them with people of good quality; nor has he stinted quality in appointing a record number of women, blacks and Hispanics. Gov. Reagan's appointments to the state bench in California were generally approved.

In economic regulation, an area where social and political ideology makes an immediate impact on public policy, President Carter has gone in for vigorous, activist and often young appointees, and he has then encouraged their inclinations to proceed along the path of tougher regulation or insistent deregulation, as the case may be. Gov. Reagan's record reveals a more business-oriented notion of where market principles work in the public interest and where federal intervention is called for, and this would presumably be reflected in his regulatory appointments. It was in California. The people who are heaping so much scorn on Mr. Reagan's shift toward the center in this campaign could, if he is elected, come to depend very heavily on his willingness to soften some of the sharper edges of his ideological commitments.