| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 733 | 2,227 | 3,031 | |
| 2020 | R | 769 | 2,068 | 2,900 | |
| 2016 | R | 623 | 1,794 | 2,587 | |
| 2012 | R | 905 | 1,655 | 2,613 | |
| 2008 | R | 1,219 | 1,646 | 2,945 | |
| 2004 | R | 1,099 | 1,242 | 2,364 | |
| 2000 | D | 1,610 | 965 | 2,631 | |
| 1996 | R | 1,166 | 1,292 | 2,723 | |
| 1992 | R | 1,167 | 1,177 | 2,984 | |
| 1988 | R | 1,492 | 1,501 | 3,002 | |
| 1984 | R | 1,448 | 1,902 | 3,362 | |
| 1980 | R | 1,223 | 2,014 | 3,544 | |
| 1976 | D | 1,822 | 1,744 | 3,578 | |
| 1972 | D | 1,993 | 1,963 | 3,963 | |
| 1968 | R | 1,653 | 1,959 | 3,800 | |
| 1964 | D | 2,181 | 1,756 | 3,937 | |
| 1960 | R | 1,797 | 2,375 | 4,172 | |
| 1956 | R | 633 | 2,225 | 2,858 | |
| 1952 | R | 1,127 | 2,991 | 4,118 | |
| 1948 | R | 1,387 | 2,064 | 3,471 | |
| 1944 | R | 1,163 | 2,516 | 3,679 | |
| 1940 | R | 1,696 | 3,310 | 5,006 | |
| 1936 | D | 2,536 | 2,117 | 4,851 | |
| 1932 | D | 2,884 | 1,436 | 4,422 | |
| 1928 | R | 1,758 | 2,234 | 4,005 | |
| 1924 | R | 457 | 1,368 | 3,090 | |
| 1920 | R | 565 | 1,864 | 3,080 | |
| 1916 | D | 1,194 | 1,021 | 2,288 | |
| 1912 | D | 962 | 0 | 2,155 | |
| 1908 | R | 826 | 1,209 | 2,121 | |
| 1904 | R | 693 | 1,284 | 2,038 | |
| 1900 | D | 989 | 978 | 1,993 | |
| 1896 | D | 1,047 | 678 | 1,737 | |
| 1892 | R | 262 | 573 | 1,534 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
McCook County's R+49.3 margin in 2024 reflects the heavily rural, agricultural character typical of southeast South Dakota, where small towns and dispersed farm households have voted consistently Republican by wide margins for decades.
The Republican margin in McCook County reached its widest at fifty-six points in 1956. The margin in 2024 was forty-nine points, in line with the county's deep historical pattern.
McCook County's loyalty is rooted in its place. Median household income of $83,852, a 93% non-Hispanic-white share, and a population of 5,751 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 Yancey County and Charles Mix County.
