Why did Ketanji Brown Jackson’s appointment not change the Supreme Court’s conservative majority?

Ketanji Brown Jackson’s appointment to the Supreme Court did not change the Court’s conservative majority because she was replacing a departing liberal justice, Stephen Breyer.1

Because Jackson was expected to be a reliably liberal vote, her confirmation simply maintained the existing ideological balance of the Court rather than shifting it. The Court’s six-to-three conservative supermajority, which had been established in 2020 following the appointment of Justice Amy Coney Barrett, remained intact after Jackson was sworn in.123