| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 47,695 | 94,562 | 144,668 | |
| 2020 | R | 50,161 | 86,469 | 139,016 | |
| 2016 | R | 31,013 | 68,212 | 106,271 | |
| 2012 | R | 25,142 | 69,850 | 96,225 | |
| 2008 | R | 27,886 | 64,858 | 93,646 | |
| 2004 | R | 21,732 | 57,451 | 79,650 | |
| 2000 | R | 18,745 | 38,901 | 58,429 | |
| 1996 | R | 15,231 | 27,699 | 45,376 | |
| 1992 | R | 13,053 | 22,015 | 40,195 | |
| 1988 | R | 7,864 | 20,847 | 28,823 | |
| 1984 | R | 6,929 | 17,975 | 24,997 | |
| 1980 | R | 8,815 | 11,597 | 21,095 | |
| 1976 | D | 8,183 | 7,880 | 16,266 | |
| 1972 | R | 2,616 | 7,556 | 10,564 | |
| 1968 | R | 2,063 | 2,788 | 9,718 | |
| 1964 | D | 5,075 | 2,707 | 7,782 | |
| 1960 | D | 4,471 | 2,699 | 7,228 | |
| 1956 | D | 4,174 | 1,979 | 6,211 | |
| 1952 | D | 4,085 | 2,326 | 6,430 | |
| 1948 | D | 2,294 | 556 | 3,861 | |
| 1944 | D | 2,656 | 602 | 3,268 | |
| 1940 | D | 3,215 | 505 | 3,746 | |
| 1936 | D | 2,769 | 286 | 3,059 | |
| 1932 | D | 2,777 | 261 | 3,087 | |
| 1928 | D | 1,595 | 693 | 2,288 | |
| 1924 | D | 1,626 | 242 | 1,916 | |
| 1920 | D | 2,004 | 946 | 2,950 | |
| 1916 | D | 2,036 | 600 | 2,646 | |
| 1912 | D | 2,205 | 797 | 3,073 | |
| 1908 | D | 1,928 | 605 | 2,561 | |
| 1904 | D | 1,932 | 475 | 2,528 | |
| 1900 | D | 2,136 | 704 | 2,927 | |
| 1896 | D | 3,097 | 1,281 | 4,446 | |
| 1892 | D | 1,992 | 575 | 3,071 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Williamson County pairs some of Tennessee's highest household incomes with one of its most lopsided presidential margins, running R+32.4 in 2024 even as rapid population growth from Nashville's sprawl continues to reshape its electorate.
The unraveling was not abrupt. The Democratic margin in Williamson County peaked at eighty-two points in 1932; it narrowed steadily over the late twentieth century. The 1980 election delivered the county to the Republican party for the first time in many years, by a margin of thirteen points. By 2024, the margin had settled into deep Republican territory.
The economic and demographic context is severe. Williamson County's median household income of $135,594 is among the lowest of any county in the United States; 5% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of Cherokee County and St. Johns County.