IF SEN. DEWARD M. KENNEDY is able to carry through with his plans to modify the "blue-slip" procedure of the Senate Judiciary Committee, he will have put another dent in that ancient and dishonorable practice known as senatorial courtesy. Even if he isn't able to do what he wants to do, Sen. Kennedy performed a useful service last week by bringing the blue-slip practice out from under the table.

The blue slip, made famous by the previous chairman of the Judiciary Committee, James O. Eastland, is an evaluation form that the committee send s to the senators from the home state of each judicial nominee. In the past, the failure of a senator to send the slip back to the committee was a signal to Chairman Eastland to kill the nomination quietly. That made it easy for a senator to exercise senatorial courtesy (they call it blackballing in less elegant clubs) against a nominee he didn't like. The senator did not have to make a sppech in opposition to the nomination, or even write a letter. All he had to do was to do nothing. His reason for vetoing a nomination could be substantial or merely personal, but he never had to express it.

Sen. Kennedy has told his colleagues on the committee that, as chairman, he will not follow Sen. Eastland's practice. If a slip is not returned, he said, he will bring the matter before the full committee for a vote on whether to proceed with a hearing or to kill the nomination. That won't end senatorial courtesty; the committee can continue to recognize it by killing all nominations on which blue slips are not returned. But it will at least get the exercise of it out into the open. The importance of that has been underlined by the way other members of the committee have responded to his proposal. They don't like it.

Instead of trying to persuade Sen. Kennedy to follow the practice originated by Sen. Eastland, the other members of the Judiciary Committee should take the next step and require any senator who wishes to invoke this misplaced veto power to appear in person and claim senatorial courtesy publicly. That would make the exercise of raw political pwer a little less attractive. Eventually, that might lead the Senate back to its proper, constitutional role in considering judicial nominations -- evaluating the nominees on their merits. In the meantime, the step that Sen. Kinnedy has taken to make the exercise of senatorial courtesy more difficult is welcome.