| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 12,661 | 11,815 | 25,130 | |
| 2020 | D | 12,345 | 11,196 | 24,566 | |
| 2016 | D | 10,440 | 10,378 | 22,707 | |
| 2012 | D | 11,296 | 9,058 | 21,061 | |
| 2008 | D | 11,967 | 9,423 | 21,850 | |
| 2004 | D | 11,555 | 10,309 | 22,318 | |
| 2000 | R | 8,477 | 8,689 | 19,138 | |
| 1996 | D | 8,012 | 5,318 | 17,279 | |
| 1992 | D | 6,472 | 5,241 | 18,529 | |
| 1988 | R | 6,402 | 8,236 | 14,778 | |
| 1984 | R | 5,289 | 8,814 | 14,166 | |
| 1980 | R | 4,883 | 6,514 | 13,140 | |
| 1976 | R | 4,853 | 6,289 | 11,633 | |
| 1972 | R | 2,941 | 6,480 | 9,422 | |
| 1968 | R | 3,525 | 4,821 | 8,580 | |
| 1964 | D | 5,397 | 3,324 | 8,723 | |
| 1960 | R | 2,845 | 6,844 | 9,689 | |
| 1956 | R | 1,384 | 6,590 | 7,974 | |
| 1952 | R | 1,545 | 6,363 | 7,925 | |
| 1948 | R | 1,469 | 4,371 | 5,890 | |
| 1944 | R | 1,807 | 4,291 | 6,104 | |
| 1940 | R | 3,214 | 5,170 | 8,398 | |
| 1936 | R | 2,678 | 5,309 | 8,172 | |
| 1932 | R | 3,907 | 4,505 | 8,467 | |
| 1928 | R | 1,402 | 4,851 | 6,294 | |
| 1924 | R | 1,125 | 4,003 | 5,281 | |
| 1920 | R | 1,666 | 4,383 | 6,128 | |
| 1916 | D | 2,539 | 2,418 | 5,082 | |
| 1912 | D | 2,145 | 881 | 4,841 | |
| 1908 | R | 1,335 | 2,491 | 3,940 | |
| 1904 | R | 1,092 | 2,248 | 3,440 | |
| 1900 | R | 1,710 | 2,469 | 4,260 | |
| 1896 | R | 1,939 | 3,253 | 5,274 | |
| 1892 | R | 2,151 | 2,503 | 4,918 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Waldo County's mix of fishing communities, small farms, and an influx of back-to-the-land residents has kept its presidential margins tight, with 2024's D+3.4 result continuing a pattern of single-digit finishes in either direction.
The county's recent history is a story of close margins. The Democratic margin reached twenty-six points in 1912; the Republican margin reached sixty-five points in 1956. Most other elections have been decided by single-digit points.
Waldo County's demographics — a population of 40,192, a 93% non-Hispanic-white share, a median household income of $72,782 — 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 Merrimack County and York County.