THE last two administrations have produced a string of mediocre Supreme Court nominees. Of the six men and one woman nominated to the court since 1980, only two can be considered truly distinguished by any standard. Compared to the pre-court accomplishments and reputations of the great justices of the past, today's nominees are a dismal bunch.Moreover, the last four nominations have resulted in four close-fought battles, one withdrawn nomination, one rejection, and one confirmation by the narrowest margin in a century - plus an R-rated confirmation hearing. It is obvious that something is wrong with the process. There are those who fault the Senate for "politicizing" the process; they suggest that the president is forced to nominate people with no track record in order to avoid what happened to Judge Robert Bork. Their underlying assumption is that the president is entitled to shape the court in his own image and that as long as the nominee is not corrupt or incompetent the Senate is obligated to confirm. That assumption is historically incorrect and politically unwise. The Constitution directs that the president shall appoint judges to the Supreme Court (as well as lower courts) with the "advice and consent" of the Senate. This was a last-minute compromise in the Federal Convention. Until two weeks before the end of the four-month-long convention, the appointment power resided in the Senate alone. All earlier suggestions to bring the president into the process failed because the delegates were worried, as Oliver Ellsworth of Massachusetts put it, that "the right to sup ersede his nomination will be ideal only [and a] nomination under such circumstances will be equivalent to an appointment." This history, plus the ordinary meaning of the terms "advice" and "consent," suggests that the Senate's role in the appointment process is every bit as broad and important as the president's. Early constitutional practice is consistent with the notion that the Senate can and should scrutinize nominees for political ideology as well as competence. The Senate rejected John Rutledge for his criticism of the Jay Treaty and Roger Taney for his role in the National Bank disputes. Both men were eminently qualified, but each was rejected solely because of his politics. Finally, the American people have signaled again and again that they have not given the president a specific "mandate" to pack the Supreme Court. Although they have elected conservative Republican presidents, they continue to elect an overwhelmingly Democratic Senate. So what is the solution to this apparent stalemate? Both the president and the Senate should take "advice and consent" seriously. The president should confer with senators of both parties before the nomination, and all concerned should be willing to compromise on ideology in the name of excellence. There are plenty of distinguished Republicans - perhaps more moderate than the president would like and more conservative than the Senate would like - who would make fine Supreme Court justices. Richard Posner and Kenneth Starr spring to mind immediately, but there are certainly others. Let's stop using the Supreme Court as a political football and concentrate on excellence. The American people, in whose name both the president and the Senate are acting, are entitled to no less.