Had it not been for his fear that a faction of liberal senators might filibuster his judicial confirmation, Richard H. Poff would have been nominated to a seat on the U.S. Supreme Court instead of William H. Rehnquist.

A conservative Republican congressman from Virginia who opposed civil rights laws, Poff was tapped by President Richard M. Nixon in 1971 in his drive to reshape the then-liberal Warren Supreme Court.

But Poff withdrew rather than subject his family to the exposure of a filibuster, and Nixon then turned to Rehn- quist, who went on to become chief justice and serve for more than three decades.

That rarely recalled event is one of several examples of how senators have used a filibuster - or more often the threat of a filibuster - as lever- age with the Senate majority or the White House in the selection of candidates for federal judgeships....

"Filibusters have always overhung the process," said Sheldon Goldman, an expert on judicial selection and political science professor at the University of Massachusetts at Amherst.

Most filibusters are threatened or unsuccessfully attempted for short-term gain, such as forcing action on other nominees or legislation, but they also have been intended to influence the choice of nominees, Goldman said.

In 1987, for example, after Sen. Jesse Helms (R-N.C.) threatened to filibuster a nomination of Anthony Kennedy, President Ronald Reagan named the more conservative Douglas Ginsberg as his choice for the Supreme Court, he said.

As it turned out, however, Ginsberg had to withdraw after revelations of his marijuana use, and Reagan ended up appointing Kennedy, who easily won confirmation.

Another example is President Bill Clinton, said Goldman. Concern about opposition, and possibly a filibuster, by Senate Republicans led him to consult with Sen. Orrin Hatch (R-Utah) and to avoid controversial choices such as then-Interior Secretary Bruce Babbitt.

Some Democrats say they began the filibusters to force Bush to consult with them and to select nominees with more moderate views.

Yet both conservative and liberal senators and activists say that the 10 successful filibusters waged by Democrats have not swayed Bush, and may even have stiffened his resolve, raising the question of whether Democrats overplayed their hand.

Sen. Jeff Sessions (R-Ala.), and other Senate Republicans said the threat of a filibuster is not likely to influence Bush in his choice to fill the first vacancy on the Supreme Court.

That opening could occur soon if Rehnquist, who has cancer, retires next month as many expect. Three other justices are over age 70....