Vice President Joe Biden re-enacts administering the Senate oath to Sen. William "Mo" Cowan, D-Mass. Thursday, Feb. 7, 2013, on Capitol Hill in Washington. Joining him, from left are. Secretary of State John Kerry, who he is replacing, Sen. Elizabeth Warren, D-Mass., his sons Miles, 8, and Grant 4, and his wife Stacey. (AP Photo/Kevin Wolf)
