| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 534 | 3,293 | 3,845 | |
| 2020 | R | 597 | 3,198 | 3,826 | |
| 2016 | R | 574 | 2,965 | 3,689 | |
| 2012 | R | 984 | 2,624 | 3,695 | |
| 2008 | R | 1,287 | 2,512 | 3,915 | |
| 2004 | R | 1,279 | 2,729 | 4,048 | |
| 2000 | R | 1,328 | 2,552 | 3,991 | |
| 1996 | R | 1,628 | 1,737 | 3,880 | |
| 1992 | D | 1,590 | 1,563 | 4,222 | |
| 1988 | R | 1,776 | 2,271 | 4,063 | |
| 1984 | R | 1,649 | 2,844 | 4,493 | |
| 1980 | R | 1,732 | 2,734 | 4,655 | |
| 1976 | R | 2,304 | 2,478 | 4,813 | |
| 1972 | R | 1,383 | 3,574 | 4,957 | |
| 1968 | R | 1,688 | 3,092 | 5,192 | |
| 1964 | D | 2,787 | 2,516 | 5,303 | |
| 1960 | R | 2,200 | 4,166 | 6,366 | |
| 1956 | R | 2,518 | 4,141 | 6,659 | |
| 1952 | R | 2,261 | 5,191 | 7,465 | |
| 1948 | R | 2,854 | 3,646 | 6,513 | |
| 1944 | R | 2,623 | 4,330 | 6,964 | |
| 1940 | R | 3,325 | 5,304 | 8,636 | |
| 1936 | R | 3,942 | 4,888 | 8,852 | |
| 1932 | D | 3,376 | 2,476 | 5,883 | |
| 1928 | R | 2,319 | 4,818 | 7,153 | |
| 1924 | R | 2,792 | 4,247 | 7,300 | |
| 1920 | R | 2,502 | 5,151 | 7,740 | |
| 1916 | R | 2,205 | 2,741 | 5,089 | |
| 1912 | R | 1,985 | 2,081 | 5,140 | |
| 1908 | R | 1,938 | 2,842 | 4,866 | |
| 1904 | R | 1,596 | 3,014 | 4,787 | |
| 1900 | R | 2,209 | 3,083 | 5,480 | |
| 1896 | R | 2,582 | 2,956 | 5,577 | |
| 1892 | R | 1,630 | 2,474 | 4,683 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Harrison County's R+71.8 margin in 2024 places it among the most one-sided counties in the state, reflecting a rural northwest Missouri demographic that has moved steadily away from competitive voting over the past two decades.
The Democratic margin in Harrison County peaked at fifteen points in 1932. By 1996 the county had flipped, voting Republican for the first time in many years. The 2024 margin was seventy-two points, the most Republican-leaning result in the county's modern history.
The economic context is the key. Harrison County's median household income of $54,367 sits well below state and national norms, and 20% of residents live below the federal poverty line. The shift here is part of a broader realignment of working-class places across the country. The county's voting pattern over the last decade is most similar to that of Craig County and Carter County.