| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 1,051 | 4,001 | 5,075 | |
| 2020 | R | 1,234 | 3,968 | 5,253 | |
| 2016 | R | 1,145 | 2,965 | 4,198 | |
| 2012 | R | 1,325 | 2,825 | 4,185 | |
| 2008 | R | 1,760 | 2,736 | 4,527 | |
| 2004 | R | 1,543 | 3,114 | 4,673 | |
| 2000 | R | 1,617 | 2,638 | 4,308 | |
| 1996 | D | 2,154 | 1,869 | 4,334 | |
| 1992 | R | 1,897 | 1,990 | 4,700 | |
| 1988 | D | 2,529 | 2,383 | 4,933 | |
| 1984 | R | 1,802 | 3,068 | 4,882 | |
| 1980 | R | 2,284 | 2,719 | 5,074 | |
| 1976 | D | 2,996 | 1,675 | 4,718 | |
| 1972 | R | 1,780 | 2,639 | 4,428 | |
| 1968 | D | 2,271 | 1,342 | 4,299 | |
| 1964 | D | 3,178 | 993 | 4,177 | |
| 1960 | D | 2,556 | 1,526 | 4,085 | |
| 1956 | R | 1,636 | 1,764 | 3,417 | |
| 1952 | R | 1,884 | 2,374 | 4,260 | |
| 1948 | D | 2,198 | 592 | 2,971 | |
| 1944 | D | 1,920 | 692 | 2,856 | |
| 1940 | D | 2,010 | 631 | 2,642 | |
| 1936 | D | 2,067 | 371 | 2,447 | |
| 1932 | D | 2,458 | 186 | 2,650 | |
| 1928 | D | 1,052 | 855 | 1,907 | |
| 1924 | D | 1,727 | 531 | 2,496 | |
| 1920 | D | 642 | 484 | 1,548 | |
| 1916 | D | 889 | 238 | 1,136 | |
| 1912 | D | 710 | 66 | 830 | |
| 1908 | — | — | — | — | |
| 1904 | — | — | — | — | |
| 1900 | — | — | — | — | |
| 1896 | — | — | — | — | |
| 1892 | — | — | — | — | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Karnes County sits atop one of the most productive Eagle Ford Shale formations, drawing energy workers to a historically agricultural landscape. Its population swings with drilling cycles, and it has delivered Republican margins above 55 points in each of the last three presidential cycles.
The unraveling was not abrupt. The Democratic margin in Karnes County peaked at eighty-six points in 1932; 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 twenty-four points. By 2024, the margin had widened further.
The economic and demographic context is severe. Karnes County's median household income of $60,214 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 Calhoun County and Refugio County.