| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 14,694 | 40,126 | 55,699 | |
| 2020 | R | 14,569 | 38,058 | 53,783 | |
| 2016 | R | 12,341 | 35,430 | 50,472 | |
| 2012 | R | 16,347 | 29,396 | 46,929 | |
| 2008 | R | 21,256 | 27,355 | 49,293 | |
| 2004 | R | 18,556 | 26,429 | 45,318 | |
| 2000 | R | 16,172 | 21,863 | 39,194 | |
| 1996 | D | 13,908 | 13,715 | 33,734 | |
| 1992 | D | 13,431 | 11,477 | 36,064 | |
| 1988 | R | 11,891 | 16,611 | 28,610 | |
| 1984 | R | 8,319 | 18,669 | 26,988 | |
| 1980 | R | 10,480 | 15,210 | 26,832 | |
| 1976 | R | 11,695 | 12,242 | 24,342 | |
| 1972 | R | 7,464 | 13,785 | 21,249 | |
| 1968 | R | 7,566 | 9,823 | 19,349 | |
| 1964 | D | 13,464 | 8,313 | 21,777 | |
| 1960 | R | 10,324 | 11,610 | 21,934 | |
| 1956 | R | 8,391 | 11,605 | 19,996 | |
| 1952 | R | 8,610 | 11,367 | 20,004 | |
| 1948 | D | 7,822 | 7,725 | 15,585 | |
| 1944 | R | 5,958 | 9,325 | 15,326 | |
| 1940 | R | 7,237 | 10,283 | 17,555 | |
| 1936 | R | 7,565 | 7,708 | 15,920 | |
| 1932 | D | 8,479 | 5,369 | 13,992 | |
| 1928 | R | 5,429 | 7,831 | 13,292 | |
| 1924 | R | 3,384 | 6,253 | 10,543 | |
| 1920 | R | 2,814 | 8,712 | 11,733 | |
| 1916 | R | 2,468 | 4,325 | 6,935 | |
| 1912 | R | 2,239 | 2,424 | 5,595 | |
| 1908 | R | 2,423 | 4,049 | 6,647 | |
| 1904 | R | 2,278 | 3,738 | 6,138 | |
| 1900 | R | 2,652 | 3,686 | 6,411 | |
| 1896 | R | 2,904 | 3,797 | 6,725 | |
| 1892 | R | 2,498 | 2,987 | 5,703 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Franklin County's R+45.9 margin in 2024 reflects a decades-long realignment among working-class exurban voters once competitive in statewide races. Its position on the outer edge of the St. Louis metro makes it a benchmark for rural-suburban drift.
The Republican margin in Franklin County reached its widest at fifty points in 1920. The margin in 2024 was forty-six points, in line with the county's deep historical pattern.
Franklin County's loyalty is rooted in its place. Median household income of $73,165, a 89% non-Hispanic-white share, and a population of 105,950 together describe a community whose political habits are deeply settled. The county's voting pattern over the last decade is most similar to that of Warren County and Clinton County.