Patrick Leahy
On December 17, 2012 after the death of Daniel Inouye, Leahy became the new President pro tempore of the United States Senate. After Inouye's death, Leahy is now the most senior Democrat in the United States. Leahy is currently the longest serving senator in the United States. He took office at a younger age than any other current senator. On January 3, 2015, Orrin Hatch succeeded Leahy as President pro tempore of the United States Senate. He was honored with the title President pro tempore emeritus soon afterwards. In 2021 after Democrats gained control of the U.S. Senate, Leahy became President pro tempore of the United States Senate again.