According to our Constitution, the President nominates, and with the consent of the Senate appoints, the judges of the Supreme Court. In only 12 of the last 30 years has a single party controlled the presidency and the Senate; therefore, only during those years has there been (largely) uni-partisan control over the selection of new members of the Supreme Court.
All nine of our justices were appointed during the last three decades. Seven, however, were chosen during those more uni-partisan years. Four were appointed under Democratic dominance: Justices Ginsburg, Breyer, Sotomayor, and Kagan. Three were appointed under Republican dominance: Justices Scalia and Alito, and Chief Justice Roberts.
The other two, Justices Thomas and Kennedy, were chosen by a Republican President and confirmed by a Democratic-controlled Senate. In Justice Thomas’s case, his 52 to 48 confirmation vote was nearly uni-partisan—and bitterly so: a handful of conservative Democrats, including future Republican Richard Shelby of Alabama, joined nearly all Republicans in (barely) consenting to Thomas’s appointment. Justice Kennedy, in contrast, was nominated by President Reagan but then unanimously endorsed by the Democratic majority in the Senate. In this respect, his appointment was peculiarly and distinctively bipartisan.