The major political groups are the Democratic and Republican parties. Minor parties have seldom affected the outcome of an election in Tennessee.
When Tennessee entered the Union in 1796, it was strongly loyal to the Democratic-Republican Party. The Jacksonian era brought a change in political affiliations, and for more than 20 years, Tennessee had a vibrant two-party system. Jackson's followers formed the Democratic Party, which prevailed for a decade over the National Republican Party led by John Quincy Adams and Henry Clay. But by 1835, Tennesseans had become disillusioned with Jackson, and they joined the new Whig Party in large numbers. A Whig governor was elected in that year, and Whig presidential nominees consistently garnered Tennessee's electoral votes until the party foundered over the slavery issue in the 1850s.
After the Civil War and Reconstruction, Tennessee was part of the solid Democratic South for nearly a century. Only three Republican governors were elected during that period, and only then because bitter factionalism had divided the dominant party. East Tennessee remained a Republican stronghold. However, the 2nd Congressional district, which includes Knoxville, was the only district in the country to elect a Republican continuously from 1860 on. Republicans Warren G. Harding and Herbert Hoover carried the state in the presidential elections of 1920 and 1928. But whereas the 1920s saw a tendency away from one-party domination, Franklin D. Roosevelt and the New Deal brought the Volunteer State decisively back into the Democratic fold. Tennesseans voted overwhelmingly Democratic in the four elections that Roosevelt won (1932–44).
After World War II, the one-party system in Tennessee was shaken anew. Dwight D. Eisenhower narrowly won the state in 1952 and 1956, although Tennessee Senator Estes Kefauver was the Democratic vice-presidential nominee in the latter year. Tennesseans chose Richard Nixon all three times he ran for president. In fact, between 1948 and 1976, the only Democratic nominees to carry the state came from the South (Lyndon Johnson and Jimmy Carter) or from a border state (Harry Truman).
In state elections, the Republicans made deep inroads into Democratic power during the 1960s and 1970s. In 1966, Howard Baker became the first popularly elected Republican US senator in the state history. In 1970, voters elected Winfield Dunn as the first Republican governor in more than 50 years, and in the same year, they sent Republican Bill Brock to join Baker in the Senate. The Democrats regained the governorship in 1974 and Brock's seat in 1976, but Republicans again won the governorship in 1978 when Lamar Alexander defeated Jacob F. "Jake" Butcher. In 1982, Alexander became the first Tennessee governor to be elected to two successive four-year terms. Ned McWherter, a Democrat, was elected governor in 1990. Republican Don Sundquist became governor in 1994 and was reelected in 1998. Democrat Phil Bredesen was elected governor in 2002.
In 1994, Bill Frist, a heart surgeon, was elected to the US Senate on the Republican ticket, defeating Democrat James Sasser. He was reelected in 2000, and elected Senate Majority Leader in December 2002 after former Majority Leader Trent Lott aroused controversy by praising the 1948 presidential candidacy of segregationist Strom Thurmond. Democrat Harlan Matthews was appointed to fill the seat vacated by Al Gore in 1992 when Gore became vice president. In 1994, Republican Fred Thompson defeated Jim Cooper for the remaining two years of Gore's term. Thompson was elected to his first full term in 1996, but retired in 2002. That November, former Governor Lamar Alexander was elected US Senator from Tennessee. US representatives included four Republicans and five Democrats after the November 2002 elections. There were 18 Democrats and 15 Republicans in the state senate and 54 Democrats and 45 Republicans in the state house in mid-2003.
Tennessee voters, who gave Republican George Bush 57.4% of the vote in 1988, chose Bill Clinton in 1992 and 1996. In 2000, Republican George W. Bush received 51% of the vote to Democrat Al Gore's 48%. In 2002 there were 3,134,104 registered voters; there is no party registration in the state. The state had 11 electoral votes in the 2000 presidential election.