| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 317,103 | 198,311 | 523,138 | |
| 2020 | D | 319,511 | 185,460 | 510,157 | |
| 2016 | D | 256,082 | 162,731 | 438,652 | |
| 2012 | D | 233,356 | 174,381 | 412,869 | |
| 2008 | D | 253,393 | 165,552 | 422,419 | |
| 2004 | D | 222,048 | 175,741 | 399,591 | |
| 2000 | D | 177,990 | 145,623 | 332,422 | |
| 1996 | D | 143,664 | 121,047 | 293,961 | |
| 1992 | D | 136,572 | 125,704 | 318,576 | |
| 1988 | R | 109,834 | 170,294 | 282,870 | |
| 1984 | R | 99,741 | 181,426 | 282,666 | |
| 1980 | R | 84,289 | 156,996 | 271,553 | |
| 1976 | R | 112,644 | 155,480 | 273,169 | |
| 1972 | R | 91,959 | 173,662 | 270,018 | |
| 1968 | R | 102,464 | 141,621 | 260,732 | |
| 1964 | D | 135,657 | 102,714 | 239,075 | |
| 1960 | R | 92,212 | 142,796 | 235,326 | |
| 1956 | R | 59,095 | 133,270 | 192,583 | |
| 1952 | R | 57,701 | 115,899 | 173,973 | |
| 1948 | R | 41,112 | 85,576 | 128,626 | |
| 1944 | R | 47,815 | 78,260 | 126,827 | |
| 1940 | R | 49,409 | 73,250 | 123,091 | |
| 1936 | R | 57,870 | 66,442 | 126,506 | |
| 1932 | R | 32,971 | 64,619 | 100,961 | |
| 1928 | R | 23,026 | 76,680 | 100,408 | |
| 1924 | R | 11,094 | 45,407 | 60,154 | |
| 1920 | R | 12,239 | 31,963 | 45,855 | |
| 1916 | R | 13,658 | 20,431 | 35,072 | |
| 1912 | D | 11,894 | 8,978 | 33,632 | |
| 1908 | R | 11,899 | 19,088 | 31,909 | |
| 1904 | R | 10,420 | 18,833 | 30,096 | |
| 1900 | R | 11,208 | 17,051 | 28,849 | |
| 1896 | R | 9,985 | 17,329 | 28,294 | |
| 1892 | D | 13,611 | 13,591 | 27,682 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Once a reliably Republican collar county, Montgomery has shifted so decisively that its 2024 presidential margin of D+22.8 now ranks among the widest in Pennsylvania, driven by high educational attainment and rapid demographic change in townships like Lower Merion.
The Democratic margin in Montgomery County has been steady. It reached its modern peak at twenty-six points in 2020; the 2024 margin was twenty-three points, still in line with the county's long pattern.
Montgomery County's political identity is inseparable from its demographic profile: a 73% non-Hispanic-white share, a median household income of $113,915, and the full diversity of a major metropolitan center. The county's voting pattern resembles other major urban centers most closely — Delaware County and Greater Bridgeport Planning Region.