| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 17,215 | 18,127 | 36,689 | |
| 2020 | R | 17,269 | 18,710 | 37,303 | |
| 2016 | R | 11,993 | 13,677 | 29,003 | |
| 2012 | D | 14,764 | 12,761 | 28,489 | |
| 2008 | D | 15,050 | 12,600 | 28,306 | |
| 2004 | D | 12,894 | 11,987 | 25,394 | |
| 2000 | D | 10,876 | 10,257 | 22,480 | |
| 1996 | D | 10,088 | 7,149 | 20,750 | |
| 1992 | D | 8,076 | 5,776 | 19,626 | |
| 1988 | D | 7,826 | 7,426 | 15,545 | |
| 1984 | R | 7,007 | 8,410 | 15,650 | |
| 1980 | R | 5,241 | 6,745 | 13,737 | |
| 1976 | D | 6,060 | 4,758 | 11,291 | |
| 1972 | R | 3,907 | 4,873 | 9,177 | |
| 1968 | D | 4,540 | 3,397 | 8,590 | |
| 1964 | D | 5,514 | 2,549 | 8,071 | |
| 1960 | D | 4,183 | 3,703 | 7,902 | |
| 1956 | R | 3,840 | 4,026 | 7,886 | |
| 1952 | D | 3,830 | 3,827 | 7,700 | |
| 1948 | D | 3,613 | 2,524 | 6,501 | |
| 1944 | D | 3,379 | 1,976 | 5,397 | |
| 1940 | D | 3,465 | 1,775 | 5,346 | |
| 1936 | D | 3,087 | 1,015 | 4,398 | |
| 1932 | D | 2,181 | 995 | 3,902 | |
| 1928 | R | 992 | 1,745 | 2,772 | |
| 1924 | R | 179 | 902 | 1,840 | |
| 1920 | R | 383 | 997 | 1,779 | |
| 1916 | D | 779 | 764 | 1,724 | |
| 1912 | D | 522 | 439 | 1,798 | |
| 1908 | R | 318 | 553 | 977 | |
| 1904 | R | 315 | 661 | 1,041 | |
| 1900 | R | 455 | 514 | 1,000 | |
| 1896 | D | 667 | 397 | 1,077 | |
| 1892 | D | 356 | 352 | 838 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Mason County's economy traces back to logging and shellfish aquaculture along Hood Canal, and its presidential margins have narrowed steadily over two decades, landing within 3 points in 2024 after voting more decisively Republican in earlier cycles.
The Democratic margin in Mason County has rarely exceeded forty-seven points in modern history; the Republican margin has rarely exceeded thirty-nine points. 2024 delivered the county to the Republican candidate by two points.
Mason County's demographics resemble the country more than they resemble most counties. A 77% non-Hispanic-white share, a 12% poverty rate, and a median household income of $83,270 — all within the broad national range. The county's voting pattern over the last decade is most similar to that of Rice County and Caroline County.