 Complete the following phrase:  As the longest-serving Democratic senator, Byrd served as President pro tempore four times when his party was in the majority: from 1989 until the Republicans won control of the Senate in 1995; for 17 days in early 2001, when the Senate was evenly split between parties and outgoing Vice President Al Gore broke the tie in favor of the Democrats; when the Democrats regained the majority in June 2001 after Senator Jim Jeffords of Vermont left the Republican Party to become an independent; and again from 2007 to his death in 2010, as a result of the 