| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 1,054 | 5,610 | 6,769 | |
| 2020 | R | 1,129 | 5,629 | 6,899 | |
| 2016 | R | 1,020 | 5,021 | 6,350 | |
| 2012 | R | 1,584 | 4,190 | 5,908 | |
| 2008 | R | 2,425 | 3,926 | 6,454 | |
| 2004 | R | 2,101 | 4,416 | 6,554 | |
| 2000 | R | 2,212 | 3,789 | 6,135 | |
| 1996 | D | 2,750 | 2,703 | 6,228 | |
| 1992 | D | 2,962 | 2,471 | 6,652 | |
| 1988 | R | 2,761 | 3,494 | 6,279 | |
| 1984 | R | 2,524 | 4,562 | 7,104 | |
| 1980 | R | 2,587 | 4,447 | 7,266 | |
| 1976 | R | 3,837 | 3,860 | 7,729 | |
| 1972 | R | 2,844 | 5,283 | 8,138 | |
| 1968 | R | 2,878 | 4,429 | 7,986 | |
| 1964 | D | 4,551 | 3,665 | 8,216 | |
| 1960 | R | 3,394 | 5,134 | 8,538 | |
| 1956 | R | 3,553 | 5,079 | 8,648 | |
| 1952 | R | 3,432 | 5,254 | 8,701 | |
| 1948 | R | 3,160 | 3,782 | 7,108 | |
| 1944 | R | 3,531 | 4,484 | 8,110 | |
| 1940 | R | 4,934 | 5,185 | 10,222 | |
| 1936 | D | 4,752 | 4,528 | 9,384 | |
| 1932 | D | 4,565 | 3,373 | 8,064 | |
| 1928 | R | 2,418 | 4,522 | 6,940 | |
| 1924 | R | 2,987 | 3,432 | 6,919 | |
| 1920 | R | 2,358 | 3,683 | 6,149 | |
| 1916 | R | 3,574 | 3,879 | 7,681 | |
| 1912 | D | 1,926 | 1,622 | 4,341 | |
| 1908 | R | 2,152 | 2,250 | 4,543 | |
| 1904 | R | 1,935 | 2,408 | 4,527 | |
| 1900 | R | 2,295 | 2,356 | 4,764 | |
| 1896 | D | 2,272 | 2,155 | 4,500 | |
| 1892 | R | 1,604 | 1,774 | 3,887 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Clay County's R+67.3 presidential margin in 2024 places it among the most one-sided counties in a state more often associated with competitive statewide races. Its population of roughly 14,500 reflects decades of rural depopulation across southeastern Illinois.
The Democratic margin in Clay County peaked at fifteen points in 1932. By 2000 the county had flipped, voting Republican for the first time in many years. The 2024 margin was sixty-seven points, the most Republican-leaning result in the county's modern history.
The economic context is the key. Clay County's median household income of $60,417 sits well below state and national norms, and 18% 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 Vernon County and Ripley County.