| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 6 | 129 | 135 | |
| 2020 | R | 8 | 151 | 159 | |
| 2016 | R | 5 | 149 | 159 | |
| 2012 | R | 5 | 139 | 145 | |
| 2008 | R | 8 | 151 | 163 | |
| 2004 | R | 18 | 137 | 156 | |
| 2000 | R | 14 | 120 | 137 | |
| 1996 | R | 46 | 97 | 182 | |
| 1992 | R | 54 | 79 | 189 | |
| 1988 | R | 64 | 111 | 175 | |
| 1984 | R | 53 | 141 | 194 | |
| 1980 | R | 55 | 144 | 205 | |
| 1976 | D | 100 | 96 | 197 | |
| 1972 | R | 75 | 143 | 219 | |
| 1968 | D | 109 | 44 | 224 | |
| 1964 | D | 180 | 34 | 214 | |
| 1960 | D | 133 | 39 | 173 | |
| 1956 | D | 177 | 46 | 224 | |
| 1952 | D | 189 | 66 | 255 | |
| 1948 | D | 231 | 6 | 241 | |
| 1944 | D | 228 | 13 | 256 | |
| 1940 | D | 266 | 23 | 289 | |
| 1936 | D | 211 | 13 | 224 | |
| 1932 | D | 224 | 4 | 228 | |
| 1928 | R | 45 | 85 | 130 | |
| 1924 | D | 83 | 4 | 87 | |
| 1920 | D | 157 | 0 | 160 | |
| 1916 | D | 47 | 3 | 50 | |
| 1912 | D | 77 | 2 | 82 | |
| 1908 | — | — | — | — | |
| 1904 | — | — | — | — | |
| 1900 | — | — | — | — | |
| 1896 | — | — | — | — | |
| 1892 | — | — | — | — | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
With fewer than 400 residents, King County recorded one of the widest presidential margins in the country in 2024, reflecting the deeply rural, ranching character of the Rolling Plains region where Democratic votes are a rare exception.
The unraveling was not abrupt. The Democratic margin in King County peaked at ninety-eight points in 1920; it narrowed steadily over the late twentieth century. The 1980 election delivered the county to the Republican party for the first time in many years, by a margin of forty-three points. By 2024, the margin had widened further.
The economic and demographic context is severe. King County's median household income of $46,645 is among the lowest of any county in the United States; 24% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of Llano County and Brown County.