Nominations to the highest court have regularly stirred controversy since the expansion of civil rights and civil liberties by the Supreme Court under Chief Justice Earl Warren during the 1950s and 1960s.
Democratic President Lyndon Johnson's 1968 nomination of Abe Fortas to be chief justice was filibustered by a coalition of Republicans and conservative Democrats. Reagan's 1987 nomination of Robert Bork was rejected by Democrats in a Senate vote.
The ideological wars started expanding on a large scale to lower courts during the last two decades, said Sheldon Goldman, a University of Massachusetts political science professor and author of "Picking Federal Judges: Lower Court Selection from Roosevelt through Reagan."
Goldman traces attempts to stymie potential future Supreme Court candidates at a lower level to Clinton's 1997 nomination of Judge Sonia Sotomayor to the New York-based Second U.S. Circuit Court of Appeals. The Republican-controlled Senate delayed a vote on her nomination for 464 days, though she was originally named to a district court by Republican President George H.W. Bush.
"One of the reasons was they were afraid she would be Supreme Court material," Goldman said.
A June 1998 Wall Street Journal editorial urging further delay of her nomination asserted that Clinton intended to "elevate her to the Supreme Court as soon as an opening occurs." Instead, Obama appointed her in 2009 to be the first Hispanic justice on the high court.
The possibility that Estrada would be the Supreme Court's first Hispanic member also worked against his 2001 nomination to the District of Columbia Circuit Court of Appeals by George W. Bush. Estrada was the first appeals court nominee to be filibustered, withdrawing from consideration after his backers fell short of the votes needed to cut off debate in 2003.
A memo from an aide to Sen. Richard Durbin, D-Ill., leaked to the Wall Street Journal said interest groups opposed to Estrada considered him "especially dangerous" in part because "the White House seems to be grooming him for a Supreme Court appointment."