U.S. Senators are waiting for President Bush to announce a replacement Supreme Court nominee, after Harriet Miers withdrew her nomination under intense pressure from Republican conservatives.  Democrats are calling on Mr. Bush to nominate a moderate to the high court.

The White House announcement that Ms. Miers had withdrawn her nomination took many on Capitol Hill by surprise.

Senator Arlen Specter of Pennsylvania is chairman of the Senate Judiciary Committee, which had planned to begin confirmation hearings for Ms. Miers next month.

"I am sorry to hear that Ms. Miers has decided to remove her name from consideration," he said.  "I think this is a sad episode in the history of Washington, D.C."

Ms. Miers' nomination appeared to run into trouble over a dispute between the White House and the Judiciary Committee relating to access to documents about her work as White House lawyer.  Senators wanted more information about Ms. Miers, who had never been a judge, but President Bush refused to release the documents, citing executive privilege.

But politics also played a role.  Conservatives in Mr. Bush's Republican party were disappointed with the nomination, and had wanted the president to name a prominent conservative with an extensive record of written opinions.

Senator Trent Lott, a Mississippi Republican, welcomed Ms. Miers' decision.

"I am just pleased that she stepped up to the realization that she should step aside," he said.  "I think it is in the president's best interests and the country's best interests."

Some Senate Democrats say pressure from hard-line conservatives is the chief reason for Ms. Miers' withdrawal. 

"I believe without any question that when the history books are written about all this, that it will show that the radical right wing of the Republican party drove this woman's nomination right out of town," said Senator Harry Reid of Nevada, the Senate's top Democrat.

But opposition Democrats were themselves divided on Ms. Miers' nomination, with a number of lawmakers' questioning her qualifications for the high court.

Among them is Senator Charles Schumer of New York.

"There are lots of nominees out there, who will be mainstream, who will be conservative, who could be consensus.  The president ought to take some time to find them," he said.

Ms. Miers, had she been confirmed, would have succeeded retiring Supreme Court Justice Sandra Day O'Connor, who has often cast the deciding vote in five-to-four rulings, on the closely divided court.  For that reason, whomever the President nominates to fill the post could change the balance of power on the high court.

Democrats, including Senator Ted Kennedy of Massachusetts, hope Mr. Bush will nominate someone they consider a moderate.

"President Bush has an opportunity now to unite the country.  In choosing the next nominee, he should listen to all Americans, not just the far right," he said.

Senate Majority Leader Bill Frist says he expects President Bush to announce another nomination in the very near future.