The U.S. Constitution states that the President "shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Judges of the Supreme Court." Most presidents nominate candidates who broadly share their ideological views, although a justice's decisions may end up being contrary to a president's expectations. Because the Constitution sets no qualifications for service as a justice, a president may nominate anyone to serve, subject to Senate confirmation.
In modern times, the confirmation process has attracted considerable attention from the press and advocacy groups, which lobby senators to confirm or to reject a nominee depending on whether their track record aligns with the group's views. The Senate Judiciary Committee conducts hearings and votes on whether the nomination should go to the full Senate with a positive, negative or neutral report. Once the committee reports out the nomination, the full Senate considers it. Rejections are relatively uncommon.