WASHINGTON, May 25 — The Senate cleared the way on Thursday for a top aide to President Bush, Brett M. Kavanaugh, to be confirmed for the federal appeals court, avoiding a partisan showdown over a nomination that had been stalled for three years. Senators voted, 67 to 30, for a floor vote on the nomination, expected on Friday. Democrats said Mr. Kavanaugh, who was on the staff of Kenneth W. Starr, the independent counsel who investigated President Bill Clinton, was too partisan and lacked the experience for the appellate bench. But the senators were unwilling to block the nomination using...