As you can tell, the table is sorted in descending order by the time in office or by the number of terms. Please scroll to the bottom of the table to see an explanation of the column heads.
| Senators | Party | ST | Cl* | DC1 | Sen2 | TIO3 | Term(s)4 |
| Inouye, Daniel K. | D | HI | III | 1959 | 1963 | 49 | 8.167 |
| Levin, Carl | D | MI | II | 1968 | 1969 | 43 | 7.167 |
| Leahy, Patrick J. | D | VT | III | 1974 | 1975 | 37 | 6.167 |
| Hatch, Orrin G. | R | UT | I | 1976 | 1977 | 35 | 5.833 |
| Lugar, Richard G. | R | IN | I | 1976 | 1977 | 35 | 5.833 |
| Baucus, Max | D | MT | II | 1978 | 1979 | 33 | 5.500 |
| Cochran, Thad | R | MS | II | 1972 | 1979 | 33 | 5.500 |
| Grassley, Chuck | R | IA | III | 1974 | 1981 | 31 | 5.167 |
| Bingaman, Jeff | D | NM | I | 1982 | 1982 | 30 | 5.000 |
| Lautenberg, Frank R. | D | NJ | II | 1982 | 1983 | 29 | 4.833 |
| Harkin, Tom | D | IA | II | 1974 | 1985 | 27 | 4.500 |
| Kerry, John F. | D | MA | II | 1984 | 1985 | 27 | 4.500 |
| McConnell, Mitch | R | KY | II | 1984 | 1985 | 27 | 4.500 |
| Rockefeller, John D., | D | WV | II | 1984 | 1985 | 27 | 4.500 |
| Conrad, Kent | D | ND | I | 1986 | 1987 | 25 | 4.167 |
| McCain, John | R | AZ | III | 1982 | 1987 | 25 | 4.167 |
| Reid, Harry | D | NV | III | 1982 | 1987 | 25 | 4.167 |
| Shelby, Richard C. | R | AL | III | 1986 | 1987 | 25 | 4.167 |
| Kohl, Herb | D | WI | I | 1988 | 1989 | 23 | 3.833 |
| Lieberman, Joseph I. | I | CT | I | 1988 | 1989 | 23 | 3.833 |
| Mikulski, Barbara A. | D | MD | III | 1986 | 1989 | 23 | 3.833 |
| Akaka, Daniel K. | D | HI | I | 1976 | 1991 | 21 | 3.500 |
| Boxer, Barbara | D | CA | III | 1983 | 1993 | 19 | 3.167 |
| Feinstein, Dianne | D | CA | I | 1992 | 1993 | 19 | 3.167 |
| Hutchison, Kay Bailey | R | TX | I | 1993 | 1993 | 19 | 3.167 |
| Senators | Party | ST | Cl* | DC1 | Sen2 | TIO3 | Term(s)4 |
| Murray, Patty | D | WA | III | 1992 | 1993 | 19 | 3.167 |
| Inhofe, James M. | R | OK | II | 1994 | 1994 | 18 | 3.000 |
| Kyl, Jon | R | AZ | I | 1987 | 1995 | 17 | 2.833 |
| Snowe, Olympia J. | R | ME | I | 1978 | 1995 | 17 | 2.833 |
| Wyden, Ron | D | OR | III | 1981 | 1996 | 16 | 2.667 |
| Collins, Susan M. | R | ME | II | 1996 | 1997 | 15 | 2.500 |
| Durbin, Richard J. | D | IL | II | 1996 | 1997 | 15 | 2.500 |
| Enzi, Michael B. | R | WY | II | 1996 | 1997 | 15 | 2.500 |
| Johnson, Tim | D | SD | II | 1986 | 1997 | 15 | 2.500 |
| Landrieu, Mary L. | D | LA | II | 1996 | 1997 | 15 | 2.500 |
| Reed, Jack | D | RI | II | 1996 | 1997 | 15 | 2.500 |
| Roberts, Pat | R | KS | II | 1980 | 1997 | 15 | 2.500 |
| Sessions, Jeff | R | AL | II | 1996 | 1997 | 15 | 2.500 |
| Crapo, Mike | R | ID | III | 1992 | 1999 | 13 | 2.167 |
| Schumer, Charles E. | D | NY | III | 1998 | 1999 | 13 | 2.167 |
| Cantwell, Maria | D | WA | I | 2000 | 2001 | 11 | 1.833 |
| Carper, Thomas R. | D | DE | I | 1982 | 2001 | 11 | 1.833 |
| Nelson, Ben | D | NE | I | 2000 | 2001 | 11 | 1.833 |
| Nelson, Bill | D | FL | I | 2000 | 2001 | 11 | 1.833 |
| Stabenow, Debbie | D | MI | I | 2000 | 2001 | 11 | 1.833 |
| Alexander, Lamar | R | TN | II | 2002 | 2003 | 9 | 1.500 |
| Chambliss, Saxby | R | GA | II | 2002 | 2003 | 9 | 1.500 |
| Cornyn, John | R | TX | II | 2002 | 2003 | 9 | 1.500 |
| Graham, Lindsey | R | SC | II | 2002 | 2003 | 9 | 1.500 |
| Murkowski, Lisa | R | AK | III | 2002 | 2003 | 9 | 1.500 |
| Senators | Party | ST | Cl* | DC1 | Sen2 | TIO3 | Term(s)4 |
| Pryor, Mark L. | D | AR | II | 2002 | 2003 | 9 | 1.500 |
| Burr, Richard | R | NC | III | 1994 | 2005 | 7 | 1.167 |
| Coburn, Tom | R | OK | III | 1994 | 2005 | 7 | 1.167 |
| DeMint, Jim | R | SC | III | 1998 | 2005 | 7 | 1.167 |
| Isakson, Johnny | R | GA | III | 1999 | 2005 | 7 | 1.167 |
| Thune, John | R | SD | III | 1996 | 2005 | 7 | 1.167 |
| Vitter, David | R | LA | III | 1999 | 2005 | 7 | 1.167 |
| Cardin, Benjamin L. | D | MD | I | 1986 | 2006 | 6 | 1.000 |
| Menendez, Robert | D | NJ | I | 1993 | 2006 | 6 | 1.000 |
| Barrasso, John | R | WY | I | 2006 | 2007 | 5 | 0.833 |
| Brown, Sherrod | D | OH | I | 2006 | 2007 | 5 | 0.833 |
| Casey, Robert P., Jr. | D | PA | I | 2006 | 2007 | 5 | 0.833 |
| Corker, Bob | R | TN | I | 2006 | 2007 | 5 | 0.833 |
| Klobuchar, Amy | D | MN | I | 2006 | 2007 | 5 | 0.833 |
| McCaskill, Claire | D | MO | I | 2006 | 2007 | 5 | 0.833 |
| Sanders, Bernard | I | VT | I | 1990 | 2007 | 5 | 0.833 |
| Tester, Jon | D | MT | I | 2006 | 2007 | 5 | 0.833 |
| Webb, Jim | D | VA | I | 2006 | 2007 | 5 | 0.833 |
| Whitehouse, Sheldon | D | RI | I | 2006 | 2007 | 5 | 0.833 |
| Begich, Mark | D | AK | II | 2008 | 2009 | 3 | 0.500 |
| Franken, Al | D | MN | II | 2008 | 2009 | 3 | 0.500 |
| Gillibrand, Kirsten E. | D | NY | I | 2008 | 2009 | 3 | 0.500 |
| Hagan, Kay R. | D | NC | II | 2008 | 2009 | 3 | 0.500 |
| Johanns, Mike | R | NE | II | 2008 | 2009 | 3 | 0.500 |
| Merkley, Jeff | D | OR | II | 2008 | 2009 | 3 | 0.500 |
| Senators | Party | ST | Cl* | DC1 | Sen2 | TIO3 | Term(s)4 |
| Risch, James E. | R | ID | II | 2008 | 2009 | 3 | 0.500 |
| Shaheen, Jeanne | D | NH | II | 2008 | 2009 | 3 | 0.500 |
| Udall, Mark | D | CO | II | 1999 | 2009 | 3 | 0.500 |
| Udall, Tom | D | NM | II | 1998 | 2009 | 3 | 0.500 |
| Warner, Mark R. | D | VA | II | 2008 | 2009 | 3 | 0.500 |
| Wicker, Roger F. | R | MS | I | 2008 | 2009 | 3 | 0.500 |
| Brown, Scott P. | R | MA | I | 2010 | 2010 | 2 | 0.333 |
| Ayotte, Kelly | R | NH | III | 2010 | 2011 | 1 | 0.167 |
| Bennet, Michael F. | D | CO | III | 2010 | 2011 | 1 | 0.167 |
| Blumenthal, Richard | D | CT | III | 2010 | 2011 | 1 | 0.167 |
| Blunt, Roy | R | MO | III | 2010 | 2011 | 1 | 0.167 |
| Boozman, John | R | AR | III | 2010 | 2011 | 1 | 0.167 |
| Coats, Daniel | R | IN | III | 1980 | 2011 | 1 | 0.167 |
| Coons, Christopher A. | D | DE | II | 2010 | 2011 | 1 | 0.167 |
| Heller, Dean | R | NV | I | 2011 | 2011 | 1 | 0.167 |
| Hoeven, John | R | ND | III | 2010 | 2011 | 1 | 0.167 |
| Johnson, Ron | R | WI | III | 2010 | 2011 | 1 | 0.167 |
| Kirk, Mark | R | IL | III | 2000 | 2011 | 1 | 0.167 |
| Lee, Mike | R | UT | III | 2010 | 2011 | 1 | 0.167 |
| Manchin, Joe, III | D | WV | I | 2010 | 2011 | 1 | 0.167 |
| Moran, Jerry | R | KS | III | 2010 | 2011 | 1 | 0.167 |
| Paul, Rand | R | KY | III | 2010 | 2011 | 1 | 0.167 |
| Portman, Rob | R | OH | III | 2010 | 2011 | 1 | 0.167 |
| Rubio, Marco | R | FL | III | 2010 | 2011 | 1 | 0.167 |
| Toomey, Patrick J. | R | PA | III | 2010 | 2011 | 1 | 0.167 |
Avg Time in Office 12.12 Years
Avg Terms Served 2.02 Terms
*class - Article I, section 3 of the Constitution requires the Senate to be divided into three classes for purposes of elections. Senators are elected to six-year terms, and every two years the members of one class—approximately one-third of the senators—face election or reelection. Terms for senators in Class I expire in 2013, Class II in 2015, and Class III in 2017.
(1) The year each Senator was elected to Congress.
(2) The year each Senator took the oath of office. If there is more than one year's difference between this date and the year elected to congress (1), that Senator was previously a Representative for that period of time.
(3) Time In Office - This is arrived at by subtracting the year elected to the Senate (2) from 2012.
(4) Terms - The Constitution sets the term of Senators at 6 years. Consequently, the number of terms is determined by dividing the TIO by 6.
