Senator Elizabeth Warren has served in the U.S. senate for just over 24 hours, but it's very likely that she'll soon be the senior senator from Massachusetts.
If Senator John Kerry is confirmed as Secretary of State as expected, Warren, who is now 98th in Senate seniority, will supplant Hawaii's Brian Schatz as the Senate's most junior “senior” senator. Schatz was sworn in on December 27 to replace the late Daniel Inouye just seven days before the state's new junior senator Mazie Hirono, who was elected in November.
The reality is that a state's delegation usually works closely together, especially when they are from the same party. So what are the advantages of being the senior member of a state's delegation? None officially; the junior/senior designation is a matter of tradition rather than law.
But according to former Senate historian Richard Baker, Senate leaders started to settling desk assignments according to seniority in the late 19th century. Desks are often passed down by tradition from home-state predecessors, so that means a state's senior senator effectively has first pick.
By Senate resolution, the desks of Daniel Webster, Henry Clay, and Jefferson Davis are assigned to the senior senators from their home states: New Hampshire, Kentucky, and Mississippi. (Webster was born in New Hampshire, but represented Massachusetts in the Senate.)
Senior Senators also traditionally have control of federal patronage appointments in their states when the President is from their party. (Many federal judicial appointments fall into this category.)
Hawaii is suffering the biggest seniority shift in the 113th Congress. The Aloha state went from a delegation with senators who were first and 21st in seniority before Inouye's death and Senator Daniel Akaka's retirement, to senators who are 87th and 93rd.
Massachusetts is likely to suffer the same fate in the next several months.