Well, what do you know…
In 1960 Democrats passed a resolution against election-year Supreme Court recess appointments.
The vote passed 52-33 with 14 Democrats not voting.
Republican senators opposed this resolution but were defeated.
Senator John F. Kennedy from Massachusetts voted with the majority.
Via David Bernstein at the Washington Post’s Volokh Conspiracy Blog:
Thanks to a VC commenter, I discovered that in August 1960, the Democrat-controlled Senate passed a resolution, S.RES. 334, “Expressing the sense of the Senate that the president should not make recess appointments to the Supreme Court, except to prevent or end a breakdown in the administration of the Court’s business.” Each of President Eisenhower’s SCOTUS appointments had initially been a recess appointment who was later confirmed by the Senate, and the Democrats were apparently concerned that Ike would try to fill any last-minute vacancy that might arise with a recess appointment.