| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 7,822 | 16,356 | 24,620 | |
| 2020 | R | 8,077 | 15,055 | 23,550 | |
| 2016 | R | 6,276 | 13,196 | 20,580 | |
| 2012 | R | 6,634 | 11,790 | 18,663 | |
| 2008 | R | 6,871 | 11,451 | 18,540 | |
| 2004 | R | 5,277 | 10,909 | 16,313 | |
| 2000 | R | 4,435 | 8,068 | 12,738 | |
| 1996 | R | 4,629 | 5,307 | 10,761 | |
| 1992 | R | 4,398 | 4,550 | 10,445 | |
| 1988 | R | 3,834 | 4,998 | 8,871 | |
| 1984 | R | 3,326 | 5,390 | 8,739 | |
| 1980 | D | 4,429 | 3,423 | 8,108 | |
| 1976 | D | 3,841 | 2,916 | 6,847 | |
| 1972 | R | 2,074 | 3,893 | 6,065 | |
| 1968 | D | 2,579 | 2,287 | 6,054 | |
| 1964 | D | 4,933 | 1,384 | 6,333 | |
| 1960 | D | 3,822 | 2,934 | 6,756 | |
| 1956 | D | 4,017 | 2,768 | 6,799 | |
| 1952 | D | 4,076 | 2,474 | 6,562 | |
| 1948 | D | 3,840 | 1,626 | 5,622 | |
| 1944 | D | 4,415 | 1,997 | 6,446 | |
| 1940 | D | 4,823 | 1,861 | 6,702 | |
| 1936 | D | 4,384 | 1,898 | 6,317 | |
| 1932 | D | 5,180 | 2,108 | 7,325 | |
| 1928 | R | 3,232 | 3,933 | 7,165 | |
| 1924 | D | 4,092 | 2,966 | 7,130 | |
| 1920 | D | 5,446 | 3,402 | 8,879 | |
| 1916 | D | 2,919 | 1,863 | 4,804 | |
| 1912 | D | 2,487 | 1,129 | 4,248 | |
| 1908 | D | 2,742 | 1,823 | 4,607 | |
| 1904 | D | 2,657 | 1,638 | 4,368 | |
| 1900 | D | 2,794 | 1,975 | 4,769 | |
| 1896 | D | 2,524 | 2,029 | 4,727 | |
| 1892 | D | 2,122 | 1,169 | 3,473 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Shelby County, once a Democratic stronghold in the Kentucky Bluegrass region, has shifted sharply rightward over the past two decades. Its mix of small-town residents and Louisville exurbanites produced an R+34.7 margin in 2024.
The unraveling was not abrupt. The Democratic margin in Shelby County peaked at fifty-six points in 1964; it narrowed steadily over the late twentieth century. The 1984 election delivered the county to the Republican party for the first time in many years, by a margin of twenty-four points. By 2024, the margin had settled into deep Republican territory.
The economic and demographic context is severe. Shelby County's median household income of $82,604 is among the lowest of any county in the United States; 10% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of Laramie County and Umatilla County.