| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 3,941 | 7,454 | 11,750 | |
| 2020 | R | 4,393 | 7,189 | 11,913 | |
| 2016 | R | 2,980 | 5,483 | 9,459 | |
| 2012 | R | 3,301 | 4,642 | 8,175 | |
| 2008 | R | 3,682 | 4,402 | 8,318 | |
| 2004 | R | 3,243 | 4,762 | 8,115 | |
| 2000 | R | 2,681 | 3,838 | 6,897 | |
| 1996 | R | 2,555 | 2,634 | 6,195 | |
| 1992 | D | 2,161 | 1,962 | 5,906 | |
| 1988 | R | 2,346 | 2,509 | 4,995 | |
| 1984 | R | 1,920 | 3,283 | 5,216 | |
| 1980 | R | 1,654 | 2,523 | 4,737 | |
| 1976 | R | 1,769 | 1,810 | 3,777 | |
| 1972 | R | 1,229 | 1,816 | 3,221 | |
| 1968 | R | 1,160 | 1,669 | 3,020 | |
| 1964 | D | 1,739 | 1,197 | 2,938 | |
| 1960 | R | 1,214 | 1,413 | 2,629 | |
| 1956 | R | 1,117 | 1,356 | 2,473 | |
| 1952 | R | 723 | 1,488 | 2,217 | |
| 1948 | R | 559 | 622 | 1,227 | |
| 1944 | R | 297 | 419 | 723 | |
| 1940 | D | 467 | 423 | 896 | |
| 1936 | D | 514 | 253 | 803 | |
| 1932 | D | 477 | 253 | 766 | |
| 1928 | R | 308 | 481 | 811 | |
| 1924 | R | 242 | 374 | 959 | |
| 1920 | R | 300 | 623 | 1,012 | |
| 1916 | D | 904 | 581 | 1,608 | |
| 1912 | — | — | — | — | |
| 1908 | — | — | — | — | |
| 1904 | — | — | — | — | |
| 1900 | — | — | — | — | |
| 1896 | — | — | — | — | |
| 1892 | — | — | — | — | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Jefferson County sits in Oregon's arid interior plateau, where a sparse, rural population centered on agriculture and the Warm Springs Reservation has delivered double-digit Republican presidential margins in every cycle since 2000.
The Republican margin in Jefferson County reached its widest at thirty-five points in 1952. The margin in 2024 was thirty points, in line with the county's deep historical pattern.
Jefferson County's loyalty is rooted in its place. Median household income of $76,260, a 62% non-Hispanic-white share, and a population of 25,203 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 Daviess County and Mason County.
