Probably her most noted line of inquiry, though, came up empty after a nearly eight-minute exchange with Justice Kavanaugh over whether he had discussed the special counsel investigation of Mr. Trump and Russia with any lawyers at a firm founded by a lawyer for the president.
"Be sure about your answer, sir," Ms. Harris warned the nominee in a tone that intimated she knew the answer and it was not good for Justice Kavanaugh. He responded that he was unsure, since Ms. Harris would not provide a name.
After some investigation, Justice Kavanaugh responded the next day that he had not discussed the inquiry with anyone at the firm. The issue died, and Republicans scoffed that Ms. Harris looked foolish.
"I hope the Democrats have learned from the antics of 2018 that they looked pretty bad and some of the most aggressive questioning came from Harris and some of the things that lacked any credibility whatsoever came from her," said Mr. Grassley, Republican of Iowa, who remains on the committee but is no longer chairman.
Democrats on the panel said they anticipated that Ms. Harris would join them in trying to use the hearings to showcase policy divisions with Republicans over the health care law, emphasizing the possibility that Judge Barrett could join four other conservatives on the court in overturning it. They said they expected that Ms. Harris would consult with Mr. Biden, a longtime former chairman of the Judiciary Committee, about how to approach the hearing.
They also noted that she had her hands full running for vice president and would most likely have to dip in and out of the proceedings.
"She is," Senator Mazie Hirono of Hawaii said, "a tad busy."
Nicholas Fandos contributed reporting.