| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 162,874 | 157,672 | 327,604 | |
| 2020 | D | 183,915 | 155,116 | 346,266 | |
| 2016 | D | 151,927 | 132,720 | 304,226 | |
| 2012 | D | 144,229 | 128,969 | 278,165 | |
| 2008 | D | 160,406 | 122,597 | 286,420 | |
| 2004 | R | 117,172 | 130,728 | 249,609 | |
| 2000 | R | 90,902 | 95,828 | 191,670 | |
| 1996 | D | 69,354 | 62,506 | 148,304 | |
| 1992 | D | 59,633 | 58,337 | 152,123 | |
| 1988 | R | 49,816 | 73,129 | 123,731 | |
| 1984 | R | 45,193 | 78,684 | 124,397 | |
| 1980 | R | 41,975 | 69,310 | 120,658 | |
| 1976 | R | 51,103 | 61,784 | 114,727 | |
| 1972 | R | 33,633 | 65,155 | 99,218 | |
| 1968 | R | 31,576 | 43,630 | 88,460 | |
| 1964 | D | 49,663 | 38,619 | 88,282 | |
| 1960 | R | 41,056 | 42,575 | 83,712 | |
| 1956 | R | 25,188 | 45,628 | 70,916 | |
| 1952 | R | 29,749 | 38,533 | 68,392 | |
| 1948 | R | 26,430 | 28,601 | 55,628 | |
| 1944 | R | 27,085 | 30,058 | 57,453 | |
| 1940 | R | 29,442 | 32,291 | 61,946 | |
| 1936 | D | 28,135 | 25,028 | 55,314 | |
| 1932 | D | 25,798 | 25,173 | 52,266 | |
| 1928 | R | 20,877 | 26,081 | 47,405 | |
| 1924 | R | 4,707 | 22,780 | 35,505 | |
| 1920 | R | 5,410 | 21,746 | 28,474 | |
| 1916 | R | 11,378 | 19,881 | 31,747 | |
| 1912 | D | 4,717 | 3,331 | 16,767 | |
| 1908 | R | 5,693 | 10,358 | 16,901 | |
| 1904 | R | 3,191 | 10,001 | 15,065 | |
| 1900 | R | 6,655 | 10,056 | 16,980 | |
| 1896 | R | 6,873 | 9,249 | 16,242 | |
| 1892 | R | 6,434 | 6,720 | 13,574 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Once reliably Republican exurban territory, Will County has shifted steadily toward competitive margins over two decades of population growth, landing at D+1.6 in 2024 and making it a reliable bellwether for the Chicago collar region.
The county's recent history is a story of close margins. The Democratic margin reached thirteen points in 2008; the Republican margin reached fifty-seven points in 1920. Most other elections have been decided by single-digit points.
Will County's demographics — a population of 701,462, a 62% non-Hispanic-white share, a median household income of $109,984 — situate the county close to national averages on several dimensions. The county's voting pattern over the last decade is most similar to that of Radford city and DeKalb County.