When a draft of a blockbuster Supreme Court decision overturning Roe v. Wade leaked in 2022, Vice President Kamala Harris met with Ron Klain, then the White House chief of staff, in her West Wing office. He had an idea: She should lead a new task force on abortion rights.

She seemed uncertain. “Why?” she asked.

“We need a real leader, and you’re the leader,” Mr. Klain responded.

Ms. Harris asked for time to think about it. She did not want to just give a speech without substance. And she had spent much of the previous year and a half trying to avoid being typecast as the first female vice president. But as the White House began mapping out executive actions to defend access to abortion, she began to see the possibilities and accepted the role.

It was a moment that captured the essence of the Harris vice presidency. Deliberate and disciplined, cautious and at times risk averse, she saw trapdoors around her and wanted to avoid them. She considered herself a team player, but could not always be sure the team had her best interests at heart. She gravitated to issues on which she thought she could make a difference without upstaging President Biden, but was rarely promoted as a critical player in the administration.

The court’s Dobbs v. Jackson Women’s Health Organization decision eliminating a constitutional right to abortion proved to be an issue on which Ms. Harris could take the lead, one that Mr. Biden, a churchgoing Catholic, did not feel as comfortable addressing. She found her voice as the administration’s champion of abortion rights, changing some minds among Democrats who had harbored doubts about her. And she paved the way to the moment when she will accept her party’s nomination for president this week.

Ms. Harris’s record as vice president is complex, as described in interviews with dozens of current and former administration officials and allies, some of whom spoke on the condition of anonymity to avoid alienating her or the president. She has done the dutiful things she has been asked to do. She led a labor task force and a gun safety office. She traveled to places the president had no time to visit. She has been sent to deliver private messages to the leaders of Poland and Germany and to break key tie votes in the Senate.