| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 184,642 | 120,402 | 310,913 | |
| 2020 | D | 204,032 | 123,594 | 335,675 | |
| 2016 | D | 171,095 | 109,767 | 303,520 | |
| 2012 | D | 153,757 | 129,764 | 287,493 | |
| 2008 | D | 177,242 | 118,545 | 299,105 | |
| 2004 | R | 134,352 | 139,081 | 275,295 | |
| 2000 | R | 115,058 | 120,988 | 242,164 | |
| 1996 | D | 93,315 | 93,149 | 204,764 | |
| 1992 | R | 81,693 | 99,000 | 223,987 | |
| 1988 | R | 64,327 | 114,115 | 179,633 | |
| 1984 | R | 53,947 | 118,401 | 173,224 | |
| 1980 | R | 48,287 | 96,350 | 164,853 | |
| 1976 | R | 57,741 | 92,231 | 152,894 | |
| 1972 | R | 47,416 | 92,052 | 139,812 | |
| 1968 | R | 43,409 | 68,999 | 121,903 | |
| 1964 | D | 62,785 | 58,840 | 121,667 | |
| 1960 | R | 46,941 | 67,809 | 114,899 | |
| 1956 | R | 32,279 | 66,781 | 99,189 | |
| 1952 | R | 32,353 | 54,929 | 87,427 | |
| 1948 | R | 22,192 | 39,456 | 62,368 | |
| 1944 | R | 25,453 | 35,674 | 61,310 | |
| 1940 | R | 24,965 | 38,242 | 63,461 | |
| 1936 | R | 24,524 | 27,548 | 53,675 | |
| 1932 | R | 21,139 | 23,994 | 47,122 | |
| 1928 | R | 12,252 | 26,814 | 39,587 | |
| 1924 | R | 2,008 | 18,229 | 24,150 | |
| 1920 | R | 2,321 | 15,712 | 19,096 | |
| 1916 | R | 5,447 | 12,905 | 19,251 | |
| 1912 | D | 2,436 | 2,183 | 10,113 | |
| 1908 | R | 2,264 | 6,392 | 9,379 | |
| 1904 | R | 1,592 | 6,635 | 8,605 | |
| 1900 | R | 2,235 | 5,136 | 7,588 | |
| 1896 | R | 1,777 | 5,027 | 6,937 | |
| 1892 | R | 1,964 | 2,932 | 5,129 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Once a reliably Republican suburban stronghold, Lake County has shifted markedly leftward over the past decade as college-educated voters in communities like Waukegan and Lake Forest realigned, delivering a 20-point Democratic margin in 2024.
The 2008 election was the turning point, when the Democratic candidate carried the county by twenty points. The 2024 margin was twenty-one points, in line with the county's new direction.
The demographics suggest why. A population of 714,223, a 61% non-Hispanic-white share, and a median household income of $110,416 situate the county in the broader realignment patterns of recent cycles. The county's voting pattern over the last decade is most similar to that of Ventura County and Prince William County.
