| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 6,219 | 9,661 | 16,079 | |
| 2020 | R | 6,285 | 8,833 | 15,380 | |
| 2016 | R | 5,636 | 7,366 | 13,687 | |
| 2012 | D | 7,605 | 5,707 | 13,481 | |
| 2008 | D | 8,321 | 4,808 | 13,314 | |
| 2004 | D | 8,075 | 5,878 | 14,062 | |
| 2000 | D | 6,678 | 5,002 | 12,168 | |
| 1996 | D | 5,848 | 3,035 | 10,794 | |
| 1992 | D | 6,218 | 3,577 | 13,012 | |
| 1988 | D | 6,212 | 4,902 | 11,175 | |
| 1984 | R | 5,407 | 6,008 | 11,500 | |
| 1980 | R | 5,390 | 5,992 | 12,101 | |
| 1976 | D | 6,218 | 5,341 | 11,722 | |
| 1972 | R | 4,232 | 5,723 | 10,095 | |
| 1968 | R | 3,971 | 4,861 | 9,589 | |
| 1964 | D | 6,320 | 3,264 | 9,589 | |
| 1960 | R | 5,223 | 5,539 | 10,781 | |
| 1956 | R | 4,602 | 5,476 | 10,094 | |
| 1952 | R | 4,021 | 6,501 | 10,548 | |
| 1948 | D | 4,711 | 3,650 | 8,463 | |
| 1944 | R | 4,496 | 4,719 | 9,242 | |
| 1940 | R | 5,175 | 5,319 | 10,579 | |
| 1936 | D | 5,929 | 3,339 | 9,832 | |
| 1932 | D | 5,786 | 2,874 | 8,759 | |
| 1928 | R | 2,963 | 5,596 | 8,613 | |
| 1924 | R | 373 | 2,083 | 6,664 | |
| 1920 | R | 718 | 4,748 | 5,636 | |
| 1916 | R | 1,578 | 2,138 | 3,815 | |
| 1912 | R | 1,235 | 1,763 | 3,948 | |
| 1908 | R | 1,085 | 3,733 | 4,957 | |
| 1904 | R | 981 | 3,560 | 4,713 | |
| 1900 | R | 1,190 | 3,364 | 4,723 | |
| 1896 | R | 1,394 | 3,306 | 4,886 | |
| 1892 | R | 1,521 | 2,116 | 3,952 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Trempealeau County sits along the Wisconsin–Minnesota border where the Mississippi River defines both its geography and its economy. Once reliably competitive, it has shifted toward Republican presidential margins exceeding 20 points as its largely rural, non-college workforce realigned through the 2010s and 2020s.
The Democratic margin in Trempealeau County has rarely exceeded thirty-three points in modern history; the Republican margin has rarely exceeded seventy-two points. 2024 delivered the county to the Republican candidate by twenty-one points.
Trempealeau County's demographics resemble the country more than they resemble most counties. A 85% non-Hispanic-white share, a 10% poverty rate, and a median household income of $76,313 — all within the broad national range. The county's voting pattern over the last decade is most similar to that of Jackson County and Freeborn County.