Tom Clark resigned from the Supreme Court in the 1960s when Lyndon Johnson named his son, Ramsey Clark, as Attorney General. The elder Clark didn't want to have to recuse himself in many cases in which the US Government was a party. Many think that LBJ did that so he could appoint Thurgood Marshall to the Supreme Court.
That wasn't the only bit of Supreme Court hanky panky Johnson engaged in. He persuaded Arthur Goldberg to resign the Court to become UN Ambassador. Johnson wanted his buddy Abe Fortas on the Court in case a lot of his Great Society legislation came before the Court. When Johnson later tried to name Fortas Chief Justice to replace Earl Warren, Fortas' questionable ethics led to his resignation entirely. By then, Nixon was president, and he named Harry Blackmun to the Court. That move backfired somewhat (as did his later appointment of Lewis Powell), when Blackmun became one of the Court's more liberal justices (issuing the Roe v. Wade decision).