| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 5,019 | 10,196 | 15,448 | |
| 2020 | R | 5,584 | 10,478 | 16,607 | |
| 2016 | R | 5,855 | 10,456 | 16,586 | |
| 2012 | R | 6,196 | 10,699 | 17,177 | |
| 2008 | R | 6,190 | 10,677 | 17,179 | |
| 2004 | R | 7,071 | 10,502 | 17,832 | |
| 2000 | R | 6,261 | 8,647 | 15,609 | |
| 1996 | D | 8,373 | 6,053 | 15,940 | |
| 1992 | D | 8,786 | 7,305 | 18,580 | |
| 1988 | R | 5,931 | 10,581 | 17,256 | |
| 1984 | R | 6,208 | 12,333 | 18,759 | |
| 1980 | R | 6,852 | 9,401 | 17,063 | |
| 1976 | D | 8,257 | 7,918 | 16,182 | |
| 1972 | R | 3,531 | 11,925 | 15,543 | |
| 1968 | R | 4,426 | 4,919 | 17,198 | |
| 1964 | R | 6,948 | 8,472 | 15,580 | |
| 1960 | D | 6,500 | 5,631 | 13,565 | |
| 1956 | D | 7,055 | 5,059 | 12,726 | |
| 1952 | D | 7,515 | 5,266 | 12,810 | |
| 1948 | D | 5,588 | 1,039 | 8,339 | |
| 1944 | D | 4,624 | 833 | 5,459 | |
| 1940 | D | 4,842 | 489 | 5,345 | |
| 1936 | D | 4,141 | 254 | 4,408 | |
| 1932 | D | 5,429 | 245 | 5,738 | |
| 1928 | D | 3,128 | 1,612 | 4,748 | |
| 1924 | D | 1,967 | 450 | 2,673 | |
| 1920 | D | 1,967 | 493 | 2,520 | |
| 1916 | D | 1,691 | 273 | 1,964 | |
| 1912 | D | 1,090 | 152 | 1,483 | |
| 1908 | D | 1,407 | 535 | 1,965 | |
| 1904 | D | 955 | 297 | 1,260 | |
| 1900 | D | 1,238 | 336 | 1,596 | |
| 1896 | D | 1,749 | 148 | 1,957 | |
| 1892 | D | 1,431 | 106 | 1,694 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Union County anchored Arkansas's oil boom from the 1920s onward, and El Dorado remains its economic center. That extractive-industry heritage tracks closely with the county's strong Republican lean in recent cycles, with 2024 margins exceeding 33 points.
The unraveling was not abrupt. The Democratic margin in Union County peaked at ninety points in 1932; it narrowed steadily over the late twentieth century. The 2000 election delivered the county to the Republican party for the first time in many years, by a margin of fifteen points. By 2024, the margin had settled into deep Republican territory.
The economic and demographic context is severe. Union County's median household income of $55,259 is among the lowest of any county in the United States; 20% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of Columbia County and Johnson County.