| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 418 | 1,594 | 2,023 | |
| 2020 | R | 466 | 1,602 | 2,083 | |
| 2016 | R | 526 | 1,414 | 1,997 | |
| 2012 | R | 630 | 1,470 | 2,119 | |
| 2008 | R | 719 | 1,562 | 2,291 | |
| 2004 | R | 631 | 1,794 | 2,430 | |
| 2000 | R | 727 | 1,607 | 2,354 | |
| 1996 | R | 1,107 | 1,231 | 2,501 | |
| 1992 | R | 1,113 | 1,307 | 2,910 | |
| 1988 | R | 1,436 | 1,604 | 3,049 | |
| 1984 | R | 1,009 | 2,026 | 3,056 | |
| 1980 | R | 1,199 | 1,955 | 3,218 | |
| 1976 | D | 2,033 | 1,007 | 3,076 | |
| 1972 | R | 751 | 1,685 | 2,451 | |
| 1968 | D | 1,181 | 1,033 | 2,838 | |
| 1964 | D | 1,865 | 626 | 2,494 | |
| 1960 | D | 1,544 | 810 | 2,382 | |
| 1956 | D | 1,305 | 697 | 2,006 | |
| 1952 | R | 825 | 1,169 | 1,996 | |
| 1948 | D | 1,158 | 189 | 1,374 | |
| 1944 | D | 838 | 222 | 1,203 | |
| 1940 | D | 1,000 | 224 | 1,226 | |
| 1936 | D | 950 | 65 | 1,025 | |
| 1932 | D | 949 | 66 | 1,023 | |
| 1928 | D | 384 | 319 | 703 | |
| 1924 | D | 219 | 68 | 369 | |
| 1920 | D | 158 | 118 | 282 | |
| 1916 | D | 176 | 69 | 252 | |
| 1912 | D | 171 | 18 | 216 | |
| 1908 | — | — | — | — | |
| 1904 | — | — | — | — | |
| 1900 | — | — | — | — | |
| 1896 | — | — | — | — | |
| 1892 | — | — | — | — | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Castro County's flat, agricultural landscape anchors an economy built on cattle and crops, and its voters have delivered Republican presidential margins above 50 points in each of the last three cycles, reflecting the Panhandle's broader rightward consolidation.
The unraveling was not abrupt. The Democratic margin in Castro County peaked at eighty-six points in 1936; it narrowed steadily over the late twentieth century. The 1980 election delivered the county to the Republican party for the first time in many years, by a margin of twenty-three points. By 2024, the margin had widened further.
The economic and demographic context is severe. Castro County's median household income of $56,776 is among the lowest of any county in the United States; 19% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of Lynn County and Crockett County.