THE Thomas confirmation debacle raises one narrow issue and revives a broad issue about the process for confirming Supreme Court nominees.The narrow issue is how the Senate should treat a credible, serious allegation of misconduct when both the person bringing the allegation and the nominee prefer confidentiality. The Senate Judiciary Committee ought to be able to hold a full hearing - not just review an FBI report - in executive session. Its ability and inclination to do so in orderly fashion will be improved greatly if, shortly after the president makes the nomination, the committee announces a date after which new allegations (except of very recent misconduct) will not be considered. The matter should be reported to the full Senate only if the committee believes that it may bear substantially on the nominee's qualifications, and the confidentiality of the proceedings should be guarded vigilantly, as if the committee were a grand jury. The alleging witness would, of course, always retain her First Amendment right to make the allegation public if she chose; for that matter, the nominee could disclose the matter if he wished. But, where both the parties most immediately concerned prefer confidentiality, there is probably no public right to know. True, to use Justice Louis Brandeis's metaphor, sunshine is the best disinfectant. But sometimes good government thrives best when provided with a little protective shade. The broader issue is how active the Senate should be in rejecting a nominee on ideological grounds. Obviously, ideology crucially affects a Supreme Court justice's performance. Nevertheless, I believe that the nominee's views should not keep him off the court unless they are so far out of the realm of public discourse that giving him a place on the Supreme Court would embarrass the nation. Ideological rejections rarely do much good and are sometimes counterproductive - in part because they encourage the naming of "stealth" nominees rather than people of great public distinction and in part because the same president usually nominates the replacement for the rejected individual. Over the long term, for example, Anthony Kennedy is likely to join as many conservative majorities as Robert Bork would have - and perhaps more, because Kennedy is 10 years younger. Of course, theoretically the Senate could continue to reject nominees until the president named someone who satisfied it ideologically. But even if the Senate had the political will to maintain such a campaign, and even if the president were so weak as to allow his traditional prerogative to be curtailed, this would be a bad idea. Such a process would inevitably take us further along the road to making the choice of a Supreme Court justice a referendum on the hottest issue or two of the day. But the value of the Supreme Court as guardian of our liberties depends on its being distanced from ordinary majoritarian politics. But it is perfectly proper for the nominee to discuss constitutional issues, so long as he does nothing that might be construed as a commitment for the future. And the Senate would be right to reject a Supreme Court nominee's sanctimonious refusal to engage, not so his views may be checked against the litmus test of the day but so that the Senate may determine whether he will be as thoughtful and able a justice as the nation has a right to demand.