| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 8,812 | 17,443 | 26,685 | |
| 2020 | R | 9,800 | 18,233 | 28,517 | |
| 2016 | R | 8,559 | 16,621 | 26,192 | |
| 2012 | R | 8,896 | 15,937 | 25,333 | |
| 2008 | R | 8,522 | 16,457 | 25,397 | |
| 2004 | R | 8,856 | 14,747 | 23,837 | |
| 2000 | R | 8,918 | 11,981 | 21,510 | |
| 1996 | D | 10,612 | 9,316 | 21,393 | |
| 1992 | R | 8,810 | 9,158 | 20,877 | |
| 1988 | R | 7,973 | 9,685 | 17,995 | |
| 1984 | R | 6,784 | 10,185 | 17,082 | |
| 1980 | D | 7,898 | 6,779 | 15,123 | |
| 1976 | D | 6,872 | 4,270 | 11,505 | |
| 1972 | R | 2,788 | 5,469 | 9,052 | |
| 1968 | D | 3,070 | 1,675 | 9,128 | |
| 1964 | R | 2,715 | 5,085 | 7,800 | |
| 1960 | D | 4,708 | 1,377 | 6,602 | |
| 1956 | R | 1,671 | 2,417 | 4,177 | |
| 1952 | D | 2,679 | 1,086 | 3,765 | |
| 1948 | D | 914 | 286 | 2,410 | |
| 1944 | D | 1,945 | 174 | 2,119 | |
| 1940 | D | 1,550 | 153 | 1,703 | |
| 1936 | D | 1,503 | 96 | 1,599 | |
| 1932 | D | 1,429 | 86 | 1,519 | |
| 1928 | D | 1,116 | 108 | 1,224 | |
| 1924 | D | 488 | 132 | 620 | |
| 1920 | D | 183 | 92 | 275 | |
| 1916 | D | 297 | 30 | 330 | |
| 1912 | D | 157 | 28 | 210 | |
| 1908 | D | 215 | 22 | 237 | |
| 1904 | D | 313 | 12 | 325 | |
| 1900 | D | 435 | 47 | 482 | |
| 1896 | R | 125 | 282 | 418 | |
| 1892 | R | 345 | 704 | 1,049 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
St. Charles Parish lines the Mississippi River between New Orleans and Baton Rouge, its economy anchored by one of the densest concentrations of industrial plants in the country. That working-class industrial base has trended decisively Republican over recent cycles, with the 2024 presidential margin reaching R+32.3.
The unraveling was not abrupt. The Democratic margin in St. Charles Parish peaked at ninety-three points in 1904; it narrowed steadily over the late twentieth century. The 2000 election delivered the county to the Republican party for the first time in many years, by a margin of fourteen points. By 2024, the margin had settled into deep Republican territory.
The economic and demographic context is severe. St. Charles Parish's median household income of $80,897 is among the lowest of any county in the United States; 12% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of Tangipahoa Parish and Vernon Parish.
