| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 235 | 1,545 | 1,792 | |
| 2020 | R | 222 | 1,541 | 1,782 | |
| 2016 | R | 216 | 1,486 | 1,745 | |
| 2012 | R | 353 | 1,255 | 1,655 | |
| 2008 | R | 519 | 1,169 | 1,748 | |
| 2004 | R | 582 | 1,207 | 1,817 | |
| 2000 | R | 555 | 1,250 | 1,842 | |
| 1996 | D | 700 | 660 | 1,581 | |
| 1992 | D | 843 | 626 | 1,849 | |
| 1988 | D | 877 | 875 | 1,754 | |
| 1984 | R | 875 | 1,229 | 2,104 | |
| 1980 | R | 821 | 1,266 | 2,158 | |
| 1976 | D | 1,177 | 1,025 | 2,207 | |
| 1972 | R | 607 | 1,592 | 2,199 | |
| 1968 | R | 783 | 1,406 | 2,314 | |
| 1964 | D | 1,284 | 1,040 | 2,324 | |
| 1960 | R | 1,146 | 2,354 | 3,500 | |
| 1956 | R | 1,109 | 2,035 | 3,144 | |
| 1952 | R | 936 | 2,482 | 3,428 | |
| 1948 | R | 1,008 | 1,595 | 2,605 | |
| 1944 | R | 1,035 | 2,249 | 3,288 | |
| 1940 | R | 1,364 | 2,787 | 4,161 | |
| 1936 | R | 1,834 | 2,757 | 4,605 | |
| 1932 | D | 1,520 | 1,357 | 2,901 | |
| 1928 | R | 925 | 2,869 | 3,798 | |
| 1924 | R | 1,209 | 2,508 | 4,010 | |
| 1920 | R | 1,044 | 3,170 | 4,274 | |
| 1916 | R | 1,042 | 1,733 | 2,835 | |
| 1912 | R | 780 | 995 | 2,853 | |
| 1908 | R | 852 | 1,909 | 2,802 | |
| 1904 | R | 819 | 1,896 | 2,781 | |
| 1900 | R | 1,106 | 1,973 | 3,142 | |
| 1896 | R | 1,405 | 1,958 | 3,392 | |
| 1892 | R | 809 | 1,643 | 2,947 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Mercer County's 2024 presidential result — R+73.1 — places it among Missouri's most lopsided rural counties. With fewer than 4,000 residents, its voting patterns reflect the broader realignment of small agricultural communities across the northern tier of the state.
The Republican margin in Mercer County reached its widest at seventy-four points in 2020. The margin in 2024 was seventy-three points, in line with the county's deep historical pattern.
Mercer County's loyalty is rooted in its place. Median household income of $62,679, a 92% non-Hispanic-white share, and a population of 3,482 together describe a community whose political habits are deeply settled. The county's voting pattern over the last decade is most similar to that of Carroll County and DeKalb County.