President Reagan nominated Bork for associate justice of the Supreme Court on July 1, 1987, to replace retiring Associate Justice Lewis F. Powell Jr.. A hotly contested United States Senate debate over Bork's nomination ensued. Opposition was partly fueled by civil rights and women's rights groups, concerned about Bork's opposition to the authority claimed by the federal government to impose standards of voting fairness upon states (at his confirmation hearings for the position of solicitor general, he supported the rights of Southern states to impose a poll tax), and his stated desire to roll back civil rights decisions of the Warren and Burger courts. Bork is one of only four Supreme Court nominees (along with William Rehnquist, Samuel Alito, and Brett Kavanaugh) to have been opposed by the American Civil Liberties Union. Bork was also criticized for being an "advocate of disproportionate powers for the executive branch of Government, almost executive supremacy," most notably, according to critics, for his role in the 'Saturday Night Massacre'.