Specifically, when a President nominates an individual to a U.S. circuit or district court judgeship, the chairman of the committee sends a blue-colored form to the Senators representing the home state of the nominee. A home state Senator, if he or she has no objection to a nominee, returns the blue slip with a positive response. There have also been recent years, however, during which the committee's blue slip policy prevented, at times, a single Senator from having an absolute veto over the fate of judicial nominees from his or her state. The blue slip process is not codified in the Judiciary Committee's rules, and is instead a policy set by the chairman of the committee. During this period, which encompassed both unified and divided party control of the presidency and the Senate, if a home state Senator had some objection to the nominee and wanted to stop committee action, he or she could decide not to return the blue slip or return it with a negative response. Since 1979, the blue slip policy used the Judiciary Committee has varied. There have been recent years when the blue slip policy used by the Senate Judiciary Committee stopped consideration of any nomination for which a home state Senator did not return a positive blue slip. The Obama Presidency

During the Obama presidency, the policy of both Senator Patrick Leahy (chairman of the Judiciary Committee from 2009-2014) and Senator Chuck Grassley (chairman from 2015-2016) was to preclude consideration of a U.S. circuit or district court nomination by the committee if the nomination did not receive two positive blue slips from the nominee's home state Senators. The George W. Bush Presidency

Most recently, from 2003-2004 during the George W. Bush presidency, the policy of Senator Hatch was to "give great weight to negative blue slips" but, in some instances, to allow a nomination opposed by home state Senators to receive a committee hearing and committee vote (which could result in the nomination being reported to the full Senate without the support of one or both home state Senators). For one circuit court nomination, the committee held hearings and a vote. How have Senators viewed the role of "consultation" with a President in the blue slip process used for U.S. circuit and district court nominations? These circumstances were identified in a letter to Charles Ruff, counsel to the President, and included the following: 
(1) failure to give serious consideration to individuals proposed by home state Senators as possible nominees;
(2) failure to identify to home state Senators and the Judiciary Committee an individual the President is considering nominating with enough time to allow the Senator to provide meaningful feedback before any formal clearance (i.e., by the [American Bar Association] or [Federal Bureau of Investigation]) on the prospective nominee is initiated;
(3) after having identified the name of an individual the President is considering nominating, failure to (a) seek a home state Senator's feedback, including any objections the Senator may have to the prospective nominee, at least two weeks before any formal clearances are initiated, and (b) give that feedback serious consideration;
(4) failure to notify a home state Senator, and the Judiciary Committee, that formal clearance on a prospective nominee is being initiated despite the Senator's objections; and 
(5) failure to notify home state Senators, and the Judiciary Committee, before a nomination is actually made, that the President will nominate an individual. Circuit Court candidates? Senators have generally exerted less influence over the selection of circuit court nominees than over the selection of district court nominees. The lesser role for Senators, and the more independent role of the President, in the selection of circuit court nominees is well established by custom. That role of a home state Senator once the nomination is submitted is determined by the chairman's blue slip policy. Other Senators have suggested, however, that the committee's blue slip policy should not distinguish between circuit and district court nominations. The blue slip policy, however, has changed over time and may change at some point during the current presidency, or during a future one, in ways that reduce the role of home state Senators in the blue slip process for U.S. circuit and district court nominations. A blue slip policy that lessens or eliminates the ability of home state Senators to block, at least occasionally, judicial nominees they oppose might have consequences for the Senate as an institution, as well as consequences for the judicial confirmation process itself.
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 and much of the George W. Bush presidency—during periods of both unified and divided party control.
During other years, a chairman's blue slip policy has allowed for a nomination to proceed in committee—and, at times, to the Senate floor—even if the nominee did not have the support of one or both home state Senators. Since at least 1956, however, regardless of the particular blue slip policy used by the committee to process judicial nominations, it has been relatively rare for the Senate to confirm a nominee not supported by his or her home state Senators.
Historically, a committee's blue slip policy has applied to both U.S. circuit and district court nominations. Senators, however, have traditionally exerted less influence over the selection of circuit court nominees than over district court nominees. The lesser role for Senators, and the more independent role of the President, in the selection of circuit court nominees is well established by custom. While home state Senators have historically exerted less influence over the selection of circuit court nominees, they have nonetheless often retained certain prerogatives under the committee's blue slip policy once a circuit court nominee is selected by a President. For example, during the Obama presidency and much of the George W. Bush presidency, a circuit court nomination did not proceed in committee unless it had received two positive blue slips from a nominee's home state Senators.
Future changes to the committee's blue slip policy, whether during the current presidency or a future one, might have several consequences—some of which might be viewed as adverse, others which might be viewed as beneficial—to the institutional role of the Senate, as well as to the judicial confirmation process itself.