President Bush's choice to replace retiring Supreme Court Justice Sandra Day O'Connor could shape the outcome of battles over politically sensitive issues.
Justices serve for the rest of their lives, so a Supreme Court nomination gives the president a chance to affect the political climate of the United States for a long time after he leaves office.
Justice O'Connor's pending retirement opens a vacancy on the high court for the first time in 11 years. This is President Bush's first opportunity to name someone to the bench. Mr. Bush has said he would like the vacancy filled by the time the court's next session opens in October.
Tuesday evening's announcement is expected to set off a politically charged confirmation battle in the Senate. Conservatives want the president to name someone who shares their opposition to issues like abortion and gay marriage.
Others are calling for a moderate, citing Justice O'Connor's record as a centrist in many high-profile cases over the years. She often cast the decisive vote on the closely-divided nine-member bench in her 24 years of service.
President Bush has urged the Senate to hold a dignified confirmation process. He has asked that lawmakers not listen to special interest groups, especially those on the extremes.
Mr. Bush also says he will choose someone who "interprets the law" and does not legislate from the bench. He says the nominee will be a fair-minded individual who represents the mainstream of American law and American values, and who meets the highest standards of intellect, character and ability.
Prior to Tuesday's announcement, Mr. Bush consulted with lawmakers and other advisors to discuss the Supreme Court nomination.
Democrats have blocked some of Mr. Bush's nominees to lower courts. In May, a bi-partisan group of senators struck a deal to avoid a Republican threat to ban the use of filibusters (a parliamentary delaying tactic). As part of that deal, Democrats promised to filibuster court nominees only in extraordinary circumstances, in exchange for Republican pledges not to bar the delaying tactic.