CRS report via FAS – The Blue Slip Process for U.S. Circuit and District Court Nominations: Frequently Asked Questions, Barry J. McMillion, Analyst in American National Government. October 2, 2017.

“The blue slip process used by the Senate Judiciary Committee (the committee) for U.S. circuit and district court nominations has received renewed interest from Senators. The committee’s use of the blue slip has been, since at least 1917, a feature of its consideration of U.S. circuit and district court nominations. After a President selects a nominee for a U.S. circuit or district court judgeship, the chairman sends a blue-colored form to the Senators representing the home state of the nominee. The form seeks the home state Senators’ assessment of the nominee. If a home state Senator has no objection to a nominee, the blue slip is returned to the chairman with a positive response. If, however, a home state Senator objects to a nominee, the blue slip is either withheld or returned with a negative response. Since the use of blue slips is not codified or included in the committee’s rules, the chairman of the committee has the discretion to determine the extent to which a home state Senator’s negative, or withheld, blue slip stops a President’s judicial nomination from receiving a committee hearing and a committee vote and, consequently, whether it reaches the Senate floor. Over the century of the use of the blue slip, different chairmen have used the blue slip in different ways. During some years, a chairman has required a nominee to receive two positive blue slips from his or her home state Senators. This particular blue slip policy, for example, was in place during the eight years of the Obama presidency an d much of the George W. Bush presidency—during periods of both unified and divided party control.”