| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 408 | 2,035 | 2,463 | |
| 2020 | R | 478 | 1,974 | 2,471 | |
| 2016 | R | 526 | 1,884 | 2,486 | |
| 2012 | R | 908 | 1,610 | 2,595 | |
| 2008 | R | 1,173 | 1,607 | 2,869 | |
| 2004 | R | 1,178 | 1,880 | 3,089 | |
| 2000 | R | 1,127 | 1,877 | 3,064 | |
| 1996 | D | 1,402 | 1,275 | 3,054 | |
| 1992 | D | 1,510 | 1,326 | 3,436 | |
| 1988 | R | 1,562 | 1,897 | 3,465 | |
| 1984 | R | 1,784 | 2,306 | 4,090 | |
| 1980 | R | 1,824 | 2,412 | 4,325 | |
| 1976 | D | 2,313 | 2,141 | 4,484 | |
| 1972 | R | 1,588 | 2,611 | 4,199 | |
| 1968 | R | 1,907 | 2,332 | 4,464 | |
| 1964 | D | 2,695 | 2,052 | 4,747 | |
| 1960 | R | 2,504 | 3,202 | 5,706 | |
| 1956 | R | 2,805 | 3,357 | 6,162 | |
| 1952 | R | 3,041 | 3,746 | 6,792 | |
| 1948 | D | 3,443 | 3,140 | 6,592 | |
| 1944 | R | 3,328 | 3,611 | 6,944 | |
| 1940 | R | 3,743 | 4,080 | 7,836 | |
| 1936 | R | 3,986 | 4,019 | 8,025 | |
| 1932 | D | 4,053 | 3,373 | 7,453 | |
| 1928 | R | 3,292 | 4,183 | 7,496 | |
| 1924 | R | 3,703 | 3,885 | 7,875 | |
| 1920 | R | 3,475 | 4,576 | 8,121 | |
| 1916 | D | 2,446 | 2,420 | 4,937 | |
| 1912 | D | 2,226 | 1,819 | 4,701 | |
| 1908 | R | 2,269 | 2,389 | 4,720 | |
| 1904 | R | 2,224 | 2,474 | 4,810 | |
| 1900 | D | 2,395 | 2,386 | 4,863 | |
| 1896 | D | 2,451 | 2,393 | 4,877 | |
| 1892 | R | 2,095 | 2,173 | 4,364 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Sullivan County's R+66.1 margin in 2024 places it among Missouri's most heavily Republican jurisdictions, reflecting a broader pattern of consolidation in sparsely populated north-central Missouri farming communities where population has declined for decades.
The Democratic margin in Sullivan County peaked at fourteen points in 1964. By 2000 the county had flipped, voting Republican for the first time in many years. The 2024 margin was sixty-six points, the most Republican-leaning result in the county's modern history.
The economic context is the key. Sullivan County's median household income of $56,964 sits well below state and national norms, and 14% 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 Cottonwood County and Lake of the Woods County.