She was the second woman to ever be a cabinet member. Martin Patrick Durkin, a Democrat and president of the plumbers and steamfitters union, was selected as secretary of labor. Opposition from Senator Joseph McCarthy and others delayed Brennan's confirmation, so Eisenhower placed Brennan on the court via a recess appointment in 1956; the Senate confirmed Brennan's nomination in early 1957. Brennan joined Warren as a leader of the court's liberal bloc. Stanley Reed's retirement in 1957 created another vacancy, and Eisenhower nominated federal appellate judge Charles Evans Whittaker, who would serve on the Supreme Court for just five years before resigning. The fifth and final Supreme Court vacancy of Eisenhower's tenure arose in 1958 due to the retirement of Harold Burton. Eisenhower successfully nominated federal appellate judge Potter Stewart to succeed Burton, and Stewart became a centrist on the court. The Senate Foreign Relations Committee held a lengthy inquiry into the U-2 incident.