CHOOSING JUDGES for the federal bench is one of the president's most important prerogatives and enduring legacies. Unlike executive branch officials who serve only at the president's pleasure or until his term ends, judges have lifetime appointments to positions of great independence. The Senate's role in giving advice and consent therefore is even more critical than it would be in the case of a Cabinet member or an ambassador. Today, it is more important than ever because it is expected that by the end of his second term, President Reagan will have appointed over half the sitting federal judges.

Democrats on the Senate Judiciary Committee have complained that they are being pressed to act on judicial nominations -- which are coming at a fast rate -- and have resolved to slow down the process. There is nothing wrong with that if the committee members believe they need more time to do a responsible job. Certainly, it is not in the interests of the president's party to appear to be hustling unqualified candidates through the review.

Keep in mind, though, that the confirmation procinting a judge, and consideration of a nominee's qualifications begins many months before his name reaches the Senate. District judges, for example, are by tradition chosen by home-state senators, and none would be nominated over the strong opposition of those legislators. The FBI conducts full field investigations; the American Bar Association evaluates a nominee's professional qualifications; interest groups on the right and the left grade a candidate and make their views known at every stage.

During his first term, President Reagan's judicial nominees ran into little trouble. They were generally conservative and more white, male and wealthy than the judges appointed by his predecessor; they were also, on the whole, regarded as qualified and fair-minded. Ninety percent of the appeals court nominees had been judges or law professors. Not one was rejected by the Senate. This year, conservative ideologues -- who have already succeeded in blocking the nomination of three moderates -- are putting pressure on the administration to appoint like-minded jurists, and Senate Democrats understandably see the need to exercise careful review.

The president has the right to choose judges with whom he is philosophically compatible, and they should not be denied confirmation for this reason. But the Senate has the responsibility to reject nominees who are unqualified, dishonest or ideologically so extreme as to be unable to apply the laws and the constitution fairly. If the conscientious exercise of this responsibility takes time, so be it.