The U.S. Senate begins confirmation hearings for Supreme Court Chief Justice nominee John Roberts on Monday (September 12th). Judge Roberts is sure to face tough questioning on his previous work, as well as his positions on highly political issues, such as abortion and the right to privacy. His supporters and opponents have already made their opinions known and will likely intensify their rhetoric while the hearings are underway. Amy Katz takes a closer look at why a Supreme Court nominee generates so much interest, concern and debate.

The choice of any new justice is important because the Supreme Court is the most important court in the U.S., according to Judith Schaeffer, the Deputy Director of People for the American Way, a liberal advocacy and lobbying organization in Washington, DC. "The Supreme Court has the final word on what our constitution means, it has the final word in any lawsuit that it chooses to hear, and so, who sits on the Supreme Court -- and there are only nine justices -- obviously is of great importance, particularly since that appointment is for life."

Until this summer, the Supreme Court had been made up of the same nine members since 1994, the longest joint service in history, says Michael Greve, a scholar at the  American Enterprise Institute in Washington, DC. "What that means is that those justices knew each other well. They know, in advance, what everyone else is doing, so with a result that one new appointment here is not just one new appointment. We're going to get a whole new Supreme Court. How that shakes out, nobody knows in advance, but it is to be expected that we are in for a very turbulent time on the court."

U.S. President George W. Bush nominated Judge John G. Roberts to be the next Chief Justice after William Rehnquist died last week. Judge Roberts is known to be conservative. So, if he is confirmed, the ideological balance of the court will not change.

But, when President Bush nominates someone to take the place of Sandra Day O'Connor, who resigned earlier in the summer, it is possible that the court could shift to the right.

Though Republican Party President Ronald Reagan appointed her, Ms. O'Connor became a swing vote on an ideologically divided Supreme Court. She often cast the deciding vote on highly contentious issues. That surely will be different if President Bush nominates a very conservative judge to take her place.

Mr. Greve says it?s a controversial topic, "Many of these questions are extremely controversial, from abortion to gay rights, to the authority of the federal government over the states, and so on and so forth."

Ms. Schaeffer says of the important decisions made by justices, "So many of the most important decisions in the last few years have been decisions, be they good decisions or bad decisions, on religious liberty, reproductive freedom, and privacy. Justice O'Connor was the classic swing justice."

Mr. Greve adds, "On some of these questions there is a reasonable suspicion or a reasonable hint that a new appointment might swing those decisions the other way. And so that is why people on both sides of the political aisle are intently following this and agitating over it."

So, whomever President Bush nominates to replace Justice O'Connor is likely to face intense questioning and it won't be the first time. In 1987, President Ronald Reagan nominated conservative Judge Robert Bork to replace retiring Justice Lewis F. Powell.

The nomination fueled an unprecedented lobbying campaign by conservative and liberal groups. The debate in the Senate was harsh, with strong political overtones. Ultimately Judge Bork's nomination was rejected.

The outcome was different in the equally contentious confirmation hearings for Justice Clarence Thomas. President George Herbert Walker Bush nominated him, to replace the retiring Thurgood Marshall. Minority groups were strongly opposed to Justice Thomas because of his views on civil rights.

Charges of sexual misconduct surfaced, and became the focus of prolonged hearings. But without convincing proof of the charges, the Senate ultimately voted to confirm Clarence Thomas -- who still sits on the court.