| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 4,116 | 12,409 | 16,762 | |
| 2020 | R | 4,524 | 12,678 | 17,494 | |
| 2016 | R | 4,369 | 11,859 | 17,098 | |
| 2012 | R | 6,225 | 9,248 | 15,820 | |
| 2008 | R | 8,345 | 8,691 | 17,364 | |
| 2004 | R | 7,694 | 9,413 | 17,224 | |
| 2000 | R | 8,068 | 8,240 | 16,663 | |
| 1996 | D | 7,792 | 5,999 | 15,763 | |
| 1992 | D | 9,669 | 5,764 | 18,883 | |
| 1988 | R | 8,592 | 8,695 | 17,373 | |
| 1984 | R | 7,599 | 11,300 | 18,945 | |
| 1980 | R | 6,990 | 10,969 | 18,678 | |
| 1976 | D | 9,834 | 8,729 | 18,720 | |
| 1972 | R | 6,968 | 10,755 | 17,754 | |
| 1968 | R | 7,737 | 8,134 | 17,649 | |
| 1964 | D | 12,363 | 7,060 | 19,423 | |
| 1960 | R | 9,116 | 11,121 | 20,250 | |
| 1956 | R | 8,551 | 10,813 | 19,385 | |
| 1952 | R | 9,317 | 10,804 | 20,140 | |
| 1948 | D | 8,878 | 7,798 | 16,884 | |
| 1944 | D | 10,079 | 9,408 | 19,640 | |
| 1940 | D | 13,807 | 10,461 | 24,476 | |
| 1936 | D | 10,820 | 8,321 | 19,446 | |
| 1932 | D | 10,791 | 6,276 | 17,380 | |
| 1928 | R | 5,823 | 9,110 | 15,052 | |
| 1924 | R | 4,768 | 5,889 | 13,381 | |
| 1920 | R | 4,351 | 6,620 | 12,715 | |
| 1916 | D | 7,892 | 6,438 | 14,964 | |
| 1912 | D | 3,493 | 1,586 | 7,892 | |
| 1908 | D | 4,001 | 3,435 | 7,963 | |
| 1904 | R | 2,490 | 3,190 | 6,751 | |
| 1900 | D | 3,928 | 3,221 | 7,340 | |
| 1896 | D | 3,835 | 2,870 | 6,782 | |
| 1892 | D | 2,709 | 2,324 | 5,827 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Marion County, anchored by the small city of Centralia, has shifted sharply rightward over the past two decades; its 2024 presidential margin of R+49.5 reflects a pattern common to rural southern Illinois counties with declining manufacturing employment.
The Democratic margin in Marion County peaked at twenty-seven points in 1964. By 2000 the county had flipped, voting Republican for the first time in many years. The 2024 margin was forty-nine points, the most Republican-leaning result in the county's modern history.
The economic context is the key. Marion County's median household income of $61,240 sits well below state and national norms, and 15% 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 Randolph County and Jersey County.