| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 129,280 | 92,107 | 229,692 | |
| 2020 | D | 138,372 | 82,088 | 224,862 | |
| 2016 | D | 100,795 | 69,949 | 183,050 | |
| 2012 | D | 82,479 | 75,292 | 160,060 | |
| 2008 | D | 74,845 | 63,336 | 139,459 | |
| 2004 | R | 47,271 | 60,382 | 108,430 | |
| 2000 | R | 30,938 | 42,453 | 75,653 | |
| 1996 | R | 19,942 | 25,715 | 49,330 | |
| 1992 | R | 14,462 | 19,290 | 41,574 | |
| 1988 | R | 10,101 | 20,448 | 30,862 | |
| 1984 | R | 8,227 | 17,765 | 26,128 | |
| 1980 | R | 6,694 | 12,076 | 20,492 | |
| 1976 | R | 7,995 | 9,192 | 17,748 | |
| 1972 | R | 1,009 | 2,683 | 3,745 | |
| 1968 | R | 3,262 | 4,577 | 9,970 | |
| 1964 | D | 5,151 | 3,463 | 8,626 | |
| 1960 | R | 2,399 | 2,526 | 4,954 | |
| 1956 | R | 1,960 | 2,489 | 4,660 | |
| 1952 | R | 2,075 | 2,540 | 4,630 | |
| 1948 | D | 1,545 | 1,430 | 3,245 | |
| 1944 | D | 1,802 | 1,485 | 3,294 | |
| 1940 | D | 2,156 | 1,061 | 3,231 | |
| 1936 | D | 2,287 | 867 | 3,162 | |
| 1932 | D | 2,440 | 600 | 3,071 | |
| 1928 | D | 1,915 | 1,325 | 3,240 | |
| 1924 | D | 1,794 | 152 | 2,031 | |
| 1920 | D | 1,720 | 757 | 2,506 | |
| 1916 | D | 1,490 | 404 | 1,922 | |
| 1912 | D | 1,386 | 256 | 1,768 | |
| 1908 | D | 1,570 | 447 | 2,092 | |
| 1904 | D | 1,558 | 442 | 2,072 | |
| 1900 | D | 2,690 | 1,684 | 4,499 | |
| 1896 | D | 2,741 | 1,991 | 4,837 | |
| 1892 | D | 2,719 | 1,738 | 4,657 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Loudoun's rapid growth, driven by data-center corridor jobs and an influx of highly educated transplants, has shifted its presidential margins from R+20 in 2004 to D+16 in 2024 — a swing that tracks closely with national suburban realignment.
The 2008 election was the turning point, when the Democratic candidate carried the county by eight points. The 2024 margin was sixteen points, in line with the county's new direction.
The demographics suggest why. A population of 432,998, a 53% non-Hispanic-white share, and a median household income of $181,765 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 Hamilton County and Manassas city.
