| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 157,152 | 58,844 | 222,169 | |
| 2020 | D | 157,136 | 56,241 | 216,418 | |
| 2016 | D | 128,483 | 50,631 | 190,079 | |
| 2012 | D | 120,890 | 56,412 | 180,337 | |
| 2008 | D | 130,578 | 53,946 | 187,115 | |
| 2004 | D | 109,953 | 61,455 | 173,264 | |
| 2000 | D | 86,647 | 52,459 | 144,940 | |
| 1996 | D | 73,106 | 40,097 | 124,028 | |
| 1992 | D | 73,325 | 41,386 | 137,466 | |
| 1988 | D | 61,799 | 55,029 | 117,920 | |
| 1984 | R | 55,084 | 58,736 | 114,569 | |
| 1980 | D | 51,013 | 48,699 | 116,179 | |
| 1976 | R | 50,917 | 56,807 | 111,689 | |
| 1972 | D | 55,350 | 50,535 | 107,575 | |
| 1968 | R | 33,073 | 36,432 | 77,814 | |
| 1964 | D | 42,089 | 25,595 | 67,890 | |
| 1960 | R | 25,129 | 39,632 | 64,986 | |
| 1956 | R | 19,124 | 38,911 | 58,176 | |
| 1952 | R | 17,671 | 35,826 | 53,759 | |
| 1948 | R | 12,721 | 24,588 | 38,567 | |
| 1944 | R | 14,922 | 24,740 | 39,906 | |
| 1940 | R | 11,802 | 21,664 | 33,719 | |
| 1936 | R | 13,589 | 14,986 | 29,510 | |
| 1932 | R | 12,552 | 15,368 | 29,100 | |
| 1928 | R | 5,308 | 19,676 | 25,093 | |
| 1924 | R | 3,603 | 14,326 | 19,830 | |
| 1920 | R | 4,468 | 14,082 | 18,912 | |
| 1916 | R | 5,279 | 6,505 | 12,026 | |
| 1912 | D | 4,164 | 2,495 | 10,556 | |
| 1908 | R | 4,441 | 5,845 | 10,709 | |
| 1904 | R | 3,779 | 6,566 | 10,583 | |
| 1900 | R | 5,072 | 5,369 | 10,716 | |
| 1896 | R | 5,348 | 5,671 | 11,403 | |
| 1892 | D | 5,508 | 4,362 | 10,388 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Home to the University of Michigan in Ann Arbor, Washtenaw delivers some of the largest Democratic margins in the state, with college-educated voters and university employees forming the demographic backbone of its political tilt.
The unraveling was not abrupt. The Democratic margin in Washtenaw County peaked at forty-seven points in 2020; it narrowed steadily over the late twentieth century. The 1988 election delivered the county to the Republican party for the first time in many years, by a margin of six points. By 2024, the margin had widened further.
The economic and demographic context is severe. Washtenaw County's median household income of $89,180 is among the lowest of any county in the United States; 14% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of King County and Richmond city.