| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 120,077 | 99,260 | 223,534 | |
| 2020 | D | 130,166 | 96,775 | 231,876 | |
| 2016 | D | 103,665 | 82,734 | 199,687 | |
| 2012 | D | 90,332 | 88,335 | 181,725 | |
| 2008 | D | 106,756 | 83,963 | 193,299 | |
| 2004 | R | 73,813 | 92,065 | 167,297 | |
| 2000 | R | 60,127 | 76,996 | 141,405 | |
| 1996 | R | 47,902 | 54,375 | 114,693 | |
| 1992 | R | 44,568 | 55,684 | 127,938 | |
| 1988 | R | 36,366 | 66,283 | 103,412 | |
| 1984 | R | 31,875 | 72,655 | 105,159 | |
| 1980 | R | 29,015 | 64,106 | 103,784 | |
| 1976 | R | 34,057 | 59,275 | 95,374 | |
| 1972 | R | 27,525 | 64,546 | 92,377 | |
| 1968 | R | 26,609 | 54,144 | 87,420 | |
| 1964 | R | 40,703 | 46,391 | 87,094 | |
| 1960 | R | 31,279 | 55,389 | 86,761 | |
| 1956 | R | 20,848 | 56,009 | 76,916 | |
| 1952 | R | 24,058 | 50,801 | 74,955 | |
| 1948 | R | 21,176 | 39,284 | 60,992 | |
| 1944 | R | 23,362 | 38,689 | 62,236 | |
| 1940 | R | 25,676 | 41,949 | 67,914 | |
| 1936 | R | 28,187 | 33,491 | 63,729 | |
| 1932 | R | 24,638 | 32,934 | 58,656 | |
| 1928 | R | 16,184 | 38,236 | 54,673 | |
| 1924 | R | 3,517 | 32,717 | 42,858 | |
| 1920 | R | 4,323 | 26,832 | 32,398 | |
| 1916 | R | 9,875 | 23,868 | 35,204 | |
| 1912 | D | 4,394 | 2,415 | 19,066 | |
| 1908 | R | 4,316 | 12,840 | 18,267 | |
| 1904 | R | 2,799 | 12,638 | 16,708 | |
| 1900 | R | 5,259 | 12,031 | 17,811 | |
| 1896 | R | 4,852 | 12,133 | 17,347 | |
| 1892 | R | 5,778 | 7,977 | 14,827 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Kane County, anchored by Aurora and Elgin, has shifted steadily leftward over the past decade as its population diversified — the 2024 presidential margin of D+9.3 reflects a collar-county realignment that continues to reshape Illinois statewide math.
The county's recent history is a story of close margins. The Democratic margin reached fourteen points in 2020; the Republican margin reached sixty-nine points in 1920. Most other elections have been decided by single-digit points.
Kane County's demographics — a population of 517,255, a 58% non-Hispanic-white share, a median household income of $103,163 — 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 Charleston County and DuPage County.