| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 554,471 | 235,118 | 814,832 | |
| 2020 | D | 617,196 | 226,956 | 869,347 | |
| 2016 | D | 520,360 | 219,793 | 808,630 | |
| 2012 | D | 471,804 | 267,321 | 754,170 | |
| 2008 | D | 464,484 | 245,766 | 726,031 | |
| 2004 | D | 440,862 | 237,815 | 688,960 | |
| 2000 | D | 404,043 | 198,914 | 657,048 | |
| 1996 | D | 398,190 | 169,926 | 627,977 | |
| 1992 | D | 343,994 | 193,703 | 689,453 | |
| 1988 | D | 361,563 | 290,352 | 662,628 | |
| 1984 | D | 325,065 | 319,604 | 646,754 | |
| 1980 | D | 270,751 | 256,999 | 637,679 | |
| 1976 | D | 359,919 | 260,044 | 643,382 | |
| 1972 | D | 345,343 | 269,064 | 617,651 | |
| 1968 | D | 370,310 | 188,304 | 577,596 | |
| 1964 | D | 439,790 | 134,729 | 576,810 | |
| 1960 | D | 356,130 | 246,126 | 603,516 | |
| 1956 | R | 216,668 | 343,125 | 561,373 | |
| 1952 | R | 236,910 | 316,069 | 554,605 | |
| 1948 | D | 248,240 | 228,262 | 485,908 | |
| 1944 | R | 210,253 | 236,102 | 447,080 | |
| 1940 | R | 218,663 | 242,658 | 463,437 | |
| 1936 | R | 189,512 | 199,704 | 419,520 | |
| 1932 | R | 174,257 | 184,486 | 365,751 | |
| 1928 | R | 173,339 | 189,189 | 363,841 | |
| 1924 | R | 64,544 | 162,530 | 255,235 | |
| 1920 | R | 61,661 | 156,636 | 224,078 | |
| 1916 | R | 49,844 | 60,802 | 113,072 | |
| 1912 | D | 36,689 | 30,511 | 102,867 | |
| 1908 | R | 31,362 | 58,672 | 95,887 | |
| 1904 | R | 32,889 | 55,704 | 91,868 | |
| 1900 | R | 29,476 | 49,638 | 81,955 | |
| 1896 | R | 19,591 | 57,281 | 80,266 | |
| 1892 | R | 34,769 | 40,375 | 77,090 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Home to Cambridge, Lowell, and a dense arc of Boston suburbs, Middlesex combines elite university towns with working-class post-industrial cities to produce some of the most lopsided Democratic margins in the Northeast, hitting D+39.2 in 2024.
The Democratic margin in Middlesex County has been steady. It reached its modern peak at fifty-three points in 1964; the 2024 margin was thirty-nine points, still in line with the county's long pattern.
Middlesex County's political identity is inseparable from its demographic profile: a 67% non-Hispanic-white share, a median household income of $130,847, and the full diversity of a major metropolitan center. The county's voting pattern resembles other major urban centers most closely — Norfolk County and Orleans Parish.
