The current (2010) Senate Majority Leader is Harry Reid and the President Pro Tempore who by custom is the Senior Senator is Robert Byrd.
for 2010 it's Herb Kohl.
A junior senator has served in the senate for a shorter time than the other senator from his state; that other senator from his state is a senior senator.
Thad Cochran is the current senior U.S. Senator from Mississippi. He was first elected to the Senate in 1978. Roger Wicker is the junior U.S. Senator from Mississippi. He was first elected to the Senate in 2007.
Within the United States, a Senior Senator is the longer continuously serving senator from any state's delegation to the Senate of the United States. Every State sends two Senators to the US Senate, with a "Senior" Senator and a "Junior" Senator Colleague. If Senators are sworn in on the same day, other factors, such as being a former US Representative and the length of time served as a US Representative, or being a former Governor also factor into seniority. Seniority plays an important role within the Senate in allowing Senior Senators preference in choosing which committees they serve on. It also determines where in the Senate senators sit, and factors into the allotment of office space. Seniority also determines the ceremonial order of officials at diplomatic and social events (known as the United States order of precedence). The President pro tempore of the Senate, who presides over the Senate, is usually the most senior Senator from the current Majority Party.
Jim Inhofe (R) is the senior US senator, and his current term is 2009-2015. Thomas Coburn (R) is the junior US senator and his current term is 2011-2017.
Its Susan Collins, She is the U.S senate of Maine
You look at how long each has served in the senate. The one who has served the longest is the "senior senator."
Thad Cochran is the current senior U.S. Senator from Mississippi. He was first elected to the Senate in 1978. Roger Wicker is the junior U.S. Senator from Mississippi. He was first elected to the Senate in 2007.
Robert Byrd.
Each state has 2 senators. The one who has been in office the longest is the senior senator.
Sen. McCain is the senior senator for the state of Arizona and Sen. Obama is the junior senator for Illinois.
The US Senate has 100 members.
Harry Reid is the senior Senator from Nevada and the Senate Majority Leader.