| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 1,747 | 8,424 | 10,270 | |
| 2020 | R | 1,804 | 8,047 | 9,989 | |
| 2016 | R | 1,926 | 7,048 | 9,331 | |
| 2012 | R | 3,417 | 5,071 | 8,695 | |
| 2008 | D | 4,711 | 4,706 | 9,614 | |
| 2004 | R | 4,459 | 4,641 | 9,178 | |
| 2000 | D | 4,047 | 4,020 | 8,265 | |
| 1996 | D | 4,315 | 2,259 | 7,850 | |
| 1992 | D | 4,211 | 2,157 | 8,010 | |
| 1988 | D | 3,744 | 3,240 | 7,000 | |
| 1984 | R | 2,987 | 3,755 | 6,742 | |
| 1980 | R | 2,873 | 3,439 | 6,465 | |
| 1976 | D | 3,543 | 2,526 | 6,108 | |
| 1972 | R | 2,229 | 3,818 | 6,047 | |
| 1968 | R | 2,292 | 2,641 | 5,709 | |
| 1964 | D | 3,908 | 2,286 | 6,194 | |
| 1960 | R | 2,649 | 3,437 | 6,086 | |
| 1956 | R | 2,380 | 3,383 | 5,763 | |
| 1952 | R | 2,684 | 3,338 | 6,033 | |
| 1948 | D | 2,370 | 2,200 | 4,585 | |
| 1944 | R | 2,065 | 2,900 | 4,974 | |
| 1940 | R | 2,881 | 3,817 | 6,706 | |
| 1936 | D | 2,942 | 2,909 | 5,902 | |
| 1932 | D | 3,275 | 2,246 | 5,559 | |
| 1928 | R | 2,091 | 3,019 | 5,120 | |
| 1924 | R | 1,955 | 2,397 | 4,405 | |
| 1920 | R | 1,837 | 2,618 | 4,486 | |
| 1916 | R | 1,394 | 1,657 | 3,080 | |
| 1912 | D | 1,121 | 1,059 | 2,566 | |
| 1908 | R | 1,330 | 1,753 | 3,124 | |
| 1904 | R | 1,339 | 1,673 | 3,062 | |
| 1900 | R | 1,500 | 1,751 | 3,267 | |
| 1896 | R | 1,458 | 1,547 | 3,009 | |
| 1892 | D | 1,303 | 1,200 | 2,524 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Washington County's R+65.2 margin in 2024 places it among Missouri's most lopsided presidential results, reflecting a predominantly rural, small-town electorate with limited economic diversification and a long shift away from its historically Democratic roots.
The Democratic margin in Washington County peaked at twenty-six points in 1996. By 2012 the county had flipped, voting Republican for the first time in many years. The 2024 margin was sixty-five points, the most Republican-leaning result in the county's modern history.
The economic context is the key. Washington County's median household income of $56,043 sits well below state and national norms, and 17% 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 Harrison County and Iron County.