A vote is expected before the end of the week to confirm President Barack Obama's nominee. Kagan is in line to succeed retired Justice John Paul Stevens and become the fourth woman to sit on the court.
Nearly all Democrats and a handful of GOP senators are expected to vote for Kagan, who has served as the Obama administration's solicitor general.
Most Republicans say the former Harvard Law School dean isn't fit to be a justice because she'd let her liberal political views guide her decisions. They also criticize her lack of experience as a judge.
Proponents say she is highly qualified and could help bring consensus to the ideologically polarized court.