| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 259 | 929 | 1,212 | |
| 2020 | R | 257 | 905 | 1,185 | |
| 2016 | R | 241 | 819 | 1,123 | |
| 2012 | R | 389 | 688 | 1,115 | |
| 2008 | R | 500 | 669 | 1,207 | |
| 2004 | R | 581 | 817 | 1,426 | |
| 2000 | R | 252 | 1,667 | 1,953 | |
| 1996 | D | 1,926 | 253 | 2,284 | |
| 1992 | D | 1,267 | 225 | 1,651 | |
| 1988 | R | 770 | 815 | 1,595 | |
| 1984 | R | 611 | 1,080 | 1,695 | |
| 1980 | R | 628 | 1,178 | 1,932 | |
| 1976 | D | 1,025 | 881 | 1,912 | |
| 1972 | D | 1,074 | 1,064 | 2,145 | |
| 1968 | R | 956 | 1,024 | 2,060 | |
| 1964 | D | 1,401 | 912 | 2,313 | |
| 1960 | R | 1,249 | 1,254 | 2,503 | |
| 1956 | R | 1,302 | 1,327 | 2,629 | |
| 1952 | R | 905 | 1,761 | 2,666 | |
| 1948 | D | 1,046 | 990 | 2,061 | |
| 1944 | R | 998 | 1,212 | 2,210 | |
| 1940 | R | 1,398 | 1,732 | 3,130 | |
| 1936 | D | 1,919 | 1,174 | 3,204 | |
| 1932 | D | 2,398 | 860 | 3,281 | |
| 1928 | R | 1,321 | 1,576 | 2,914 | |
| 1924 | R | 327 | 1,184 | 2,501 | |
| 1920 | R | 517 | 1,125 | 2,255 | |
| 1916 | R | 711 | 898 | 1,693 | |
| 1912 | D | 577 | 0 | 1,554 | |
| 1908 | R | 513 | 847 | 1,468 | |
| 1904 | R | 265 | 1,013 | 1,368 | |
| 1900 | R | 549 | 628 | 1,218 | |
| 1896 | R | 500 | 530 | 1,045 | |
| 1892 | R | 95 | 564 | 1,014 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Sanborn County's roughly 2,700 residents make it one of South Dakota's least-populous jurisdictions, yet its presidential margins have run consistently above R+50 for over a decade, reflecting the heavily rural, agricultural character of the James River lowlands.
The unraveling was not abrupt. The Democratic margin in Sanborn County peaked at seventy-three points in 1996; it narrowed steadily over the late twentieth century. The 2000 election delivered the county to the Republican party for the first time in many years, by a margin of seventy-two points. By 2024, the margin had widened further.
The economic and demographic context is severe. Sanborn County's median household income of $78,750 is among the lowest of any county in the United States; 9% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of Klickitat County and Tyrrell County.
