"This controversial and partisan choice further deepens the divisions in America and profoundly undermines democratic governance. A real tragedy," Brown said.
The governor tweeted his opinion on Saturday, the same day Kavanaugh was confirmed as an associate justice in a climactic 50-48 roll call vote. The two-vote margin is one of the narrowest ever for a Supreme Court nominee.
Brett Kavanaugh sworn in as 114th United States Supreme Court justice in private ceremony
The vote closed out a bitter struggle over Kavanaugh's nomination, inflamed by accusations that he sexually assaulted women in the 1980s. Kavanaugh forcefully denied the accusations in sworn testimony.
Other politicians in the state also expressed concern and urged the public to go out and vote.