| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 8,015 | 12,969 | 21,257 | |
| 2020 | R | 7,475 | 12,356 | 20,115 | |
| 2016 | R | 6,180 | 10,622 | 17,696 | |
| 2012 | R | 6,109 | 9,896 | 16,337 | |
| 2008 | R | 7,333 | 9,859 | 17,400 | |
| 2004 | R | 5,700 | 10,334 | 16,123 | |
| 2000 | R | 4,209 | 8,523 | 13,175 | |
| 1996 | R | 3,658 | 6,570 | 11,724 | |
| 1992 | R | 3,623 | 6,362 | 12,265 | |
| 1988 | R | 3,163 | 7,912 | 11,136 | |
| 1984 | R | 2,747 | 7,792 | 10,579 | |
| 1980 | R | 2,687 | 6,798 | 10,256 | |
| 1976 | R | 3,405 | 6,309 | 9,902 | |
| 1972 | R | 2,278 | 6,905 | 9,385 | |
| 1968 | R | 2,178 | 6,422 | 9,215 | |
| 1964 | R | 4,262 | 4,944 | 9,216 | |
| 1960 | R | 1,993 | 7,466 | 9,472 | |
| 1956 | R | 1,844 | 6,620 | 8,478 | |
| 1952 | R | 1,610 | 6,558 | 8,181 | |
| 1948 | R | 1,442 | 5,058 | 6,587 | |
| 1944 | R | 1,704 | 5,585 | 7,330 | |
| 1940 | R | 2,220 | 5,612 | 7,857 | |
| 1936 | R | 2,946 | 5,589 | 8,602 | |
| 1932 | R | 1,948 | 3,534 | 5,734 | |
| 1928 | R | 765 | 5,708 | 6,527 | |
| 1924 | R | 1,209 | 3,707 | 5,178 | |
| 1920 | R | 1,155 | 3,305 | 4,630 | |
| 1916 | R | 1,272 | 1,902 | 3,276 | |
| 1912 | D | 1,126 | 470 | 3,465 | |
| 1908 | R | 1,154 | 2,547 | 3,808 | |
| 1904 | R | 1,034 | 2,548 | 3,679 | |
| 1900 | R | 1,359 | 2,810 | 4,269 | |
| 1896 | R | 1,186 | 2,585 | 3,939 | |
| 1892 | R | 1,569 | 2,308 | 3,978 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Union County's small population and agricultural economy anchor a reliably conservative electorate; the Republican presidential candidate has carried it by double digits in every contest since 2000, with the margin expanding notably in recent cycles.
The Republican margin in Union County reached its widest at seventy-six points in 1928. The margin in 2024 was twenty-three points, in line with the county's deep historical pattern.
Union County's loyalty is rooted in its place. Median household income of $76,404, a 89% non-Hispanic-white share, and a population of 42,456 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 Fauquier County and Aiken County.