Senate Minority Leader Mitch McConnell said on Thursday that he will not vote to confirm Judge Ketanji Brown Jackson to serve on the U.S. Supreme Court.

While the Kentucky Republican said that he had an “open mind” going into the process, he said that after examining her “record and watching her performance this week,” he “cannot and will not” back confirming her to a lifetime appointment to the high court.

Last month, President Joe Biden nominated Jackson to fill the vacancy that will arise once Justice Stephen Breyer steps down later this year.