Senators have been elected by popular vote since 1914, when the 17th amendment to the constitution took effect. The results of each of these elections by party is shown below as a table.
| Election | Dem | GOP | Other | D Chg | R Chg | President | Pres. Gain | 6th Yr |
| 2010 | 51 | 47 | 2 | -6 | 6 | Obama | -6 | |
| 2008 | 57 | 41 | 2 | 8 | -8 | Bush | -8 | |
| 2006 | 49 | 49 | 2 | 5 | -6 | Bush | -6 | -6 |
| 2004 | 44 | 55 | 1 | -4 | 4 | Bush | 4 | |
| 2002 | 48 | 51 | 1 | -2 | 1 | Bush | 1 | |
| 2000 | 50 | 50 | 0 | 5 | -5 | Clinton | 5 | |
| 1998 | 45 | 55 | 0 | 0 | 0 | Clinton | 0 | 0 |
| 1996 | 45 | 55 | 0 | -3 | 3 | Clinton | -3 | |
| 1994 | 48 | 52 | 0 | -9 | 9 | Clinton | -9 | |
| 1992 | 57 | 43 | 0 | 1 | -1 | Bush | -1 | |
| 1990 | 56 | 44 | 0 | 1 | -1 | Bush | -1 | |
| 1988 | 55 | 45 | 0 | 0 | 0 | Reagan | 0 | |
| 1986 | 55 | 45 | 0 | 8 | -8 | Reagan | -8 | -8 |
| 1984 | 47 | 53 | 0 | 1 | -1 | Reagan | -1 | |
| 1982 | 46 | 54 | 0 | 0 | 1 | Reagan | 1 | |
| 1980 | 46 | 53 | 1 | -12 | 12 | Carter | -12 | |
| 1978 | 58 | 41 | 1 | -3 | 3 | Carter | -3 | |
| 1976 | 61 | 38 | 1 | 1 | 0 | Ford | 0 | |
| 1974 | 60 | 38 | 2 | 4 | -4 | Ford | -4 | -4 |
| 1972 | 56 | 42 | 2 | 2 | -2 | Nixon | -2 | |
| 1970 | 54 | 44 | 2 | -3 | 1 | Nixon | 1 | |
| 1968 | 57 | 43 | 0 | -7 | 7 | Johnson | -7 | |
| 1966 | 64 | 36 | 0 | -4 | 4 | Johnson | -4 | -4 |
| 1964 | 68 | 32 | 0 | 2 | -2 | Johnson | 2 | |
| 1962 | 66 | 34 | 0 | 2 | -2 | Kennedy | 2 | |
| 1960 | 64 | 36 | 0 | -1 | 1 | Eisenhower | 1 | |
| 1958 | 65 | 35 | 0 | 16 | -12 | Eisenhower | -12 | -12 |
| 1956 | 49 | 47 | 0 | 1 | 0 | Eisenhower | 0 | |
| 1954 | 48 | 47 | 1 | 1 | -1 | Eisenhower | -1 | |
| 1952 | 47 | 48 | 1 | -2 | 1 | Truman | -2 | |
| 1950 | 49 | 47 | 0 | -5 | 5 | Truman | -5 | -5 |
| 1948 | 54 | 42 | 0 | 9 | -9 | Truman | 9 | |
| 1946 | 45 | 51 | 0 | -12 | 13 | Truman | -12 | |
| 1944 | 57 | 38 | 1 | 0 | 0 | Roosevelt | 0 | |
| 1942 | 57 | 38 | 1 | -9 | 10 | Roosevelt | -9 | |
| 1940 | 66 | 28 | 2 | -3 | 5 | Roosevelt | -3 | |
| 1938 | 69 | 23 | 4 | -7 | 7 | Roosevelt | -7 | -7 |
| 1936 | 76 | 16 | 4 | 7 | -9 | Roosevelt | 7 | |
| 1934 | 69 | 25 | 2 | 10 | -11 | Roosevelt | 10 | |
| 1932 | 59 | 36 | 1 | 12 | -12 | Hoover | -12 | |
| 1930 | 47 | 48 | 1 | 8 | -8 | Hoover | -8 | |
| 1928 | 39 | 56 | 1 | -7 | 8 | Coolidge | 8 | |
| 1926 | 46 | 48 | 1 | 5 | -6 | Coolidge | -6 | -6 |
| 1924 | 41 | 54 | 1 | -1 | 1 | Harding | 1 | |
| 1922 | 42 | 53 | 1 | 5 | -6 | Harding | -6 | |
| 1920 | 37 | 59 | 0 | -10 | 10 | Wilson | -10 | |
| 1918 | 47 | 49 | 0 | -7 | 7 | Wilson | -7 | -7 |
| 1916 | 54 | 42 | 0 | -2 | 2 | Wilson | -2 | |
| 1914 | 56 | 40 | 0 | Wilson |