WASHINGTON—The U.S. Senate on Wednesday confirmed Lily Batchelder to serve as assistant secretary for tax policy at the Treasury Department, where she will play a big role in implementing tax changes sought by President Joe Biden and congressional Democrats. Batchelder won confirmation in a 64–34 vote, with 15 Republicans voting in support of the New York University law professor. The vote gives the Treasury Department its fourth confirmed political appointee, with at least nine others still awaiting confirmation. Many of Biden’s nominees have been held up by Republican holds over unrelated policy issues. It came after a vote on cloture, which essentially limits debate on any bill or motion before the Senate and sets a 30-hour window before a final vote must be held. The process eliminates the ability of senators to filibuster, or hold the floor indefinitely, and delay a vote. Batchelder, who served as the Senate Finance Committee’s …