| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 4,107 | 9,942 | 14,574 | |
| 2020 | R | 4,254 | 10,298 | 14,944 | |
| 2016 | R | 3,249 | 8,431 | 12,968 | |
| 2012 | R | 3,973 | 7,636 | 12,070 | |
| 2008 | R | 4,613 | 7,581 | 12,594 | |
| 2004 | R | 4,428 | 8,879 | 13,519 | |
| 2000 | R | 3,577 | 7,836 | 12,076 | |
| 1996 | R | 4,379 | 5,414 | 11,345 | |
| 1992 | R | 3,990 | 4,223 | 11,588 | |
| 1988 | R | 4,682 | 5,061 | 10,090 | |
| 1984 | R | 4,134 | 6,645 | 10,829 | |
| 1980 | R | 3,677 | 6,514 | 11,272 | |
| 1976 | R | 4,280 | 5,111 | 9,829 | |
| 1972 | R | 3,272 | 5,073 | 8,985 | |
| 1968 | R | 3,409 | 3,796 | 7,747 | |
| 1964 | D | 4,929 | 2,553 | 7,489 | |
| 1960 | D | 4,081 | 3,689 | 7,770 | |
| 1956 | D | 4,389 | 3,749 | 8,138 | |
| 1952 | R | 3,526 | 4,114 | 7,663 | |
| 1948 | D | 3,808 | 2,668 | 6,698 | |
| 1944 | D | 3,951 | 2,413 | 6,424 | |
| 1940 | D | 4,500 | 2,642 | 7,196 | |
| 1936 | D | 4,643 | 1,517 | 6,712 | |
| 1932 | D | 4,450 | 1,705 | 6,350 | |
| 1928 | R | 2,154 | 3,219 | 5,444 | |
| 1924 | R | 1,816 | 2,428 | 5,663 | |
| 1920 | R | 1,899 | 2,844 | 5,020 | |
| 1916 | D | 3,086 | 2,253 | 5,665 | |
| 1912 | D | 1,090 | 671 | 3,134 | |
| 1908 | R | 1,191 | 1,510 | 2,980 | |
| 1904 | R | 775 | 1,884 | 2,996 | |
| 1900 | D | 1,646 | 1,512 | 3,292 | |
| 1896 | D | 2,155 | 1,303 | 3,487 | |
| 1892 | R | 586 | 1,008 | 2,915 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Union County's R+40 presidential margin in 2024 reflects a broader eastern Oregon pattern where ranching and timber economies correlate with some of the state's widest partisan gaps, even as the county seat of La Grande anchors a small university-town counterweight.
The Democratic margin in Union County peaked at forty-seven points in 1936. By 1968 the county had flipped, voting Republican for the first time in many years. The 2024 margin was forty points, the most Republican-leaning result in the county's modern history.
The economic context is the key. Union County's median household income of $65,661 sits well below state and national norms, and 16% 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 Crook County and Lincoln County.