| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 1,984 | 1,482 | 3,492 | |
| 2020 | D | 2,864 | 1,490 | 4,382 | |
| 2016 | D | 2,636 | 694 | 3,396 | |
| 2012 | D | 3,042 | 574 | 3,653 | |
| 2008 | D | 3,263 | 596 | 3,876 | |
| 2004 | D | 2,332 | 777 | 3,118 | |
| 2000 | D | 2,616 | 751 | 3,391 | |
| 1996 | D | 2,629 | 463 | 3,193 | |
| 1992 | D | 3,058 | 571 | 3,868 | |
| 1988 | D | 3,338 | 628 | 3,973 | |
| 1984 | D | 2,937 | 924 | 3,868 | |
| 1980 | D | 2,621 | 831 | 3,538 | |
| 1976 | D | 1,822 | 735 | 2,578 | |
| 1972 | R | 1,122 | 1,288 | 2,432 | |
| 1968 | D | 1,307 | 693 | 2,215 | |
| 1964 | D | 1,784 | 598 | 2,385 | |
| 1960 | R | 706 | 761 | 1,475 | |
| 1956 | R | 528 | 896 | 1,427 | |
| 1952 | R | 677 | 1,043 | 1,723 | |
| 1948 | D | 618 | 306 | 986 | |
| 1944 | D | 696 | 342 | 1,129 | |
| 1940 | D | 739 | 259 | 998 | |
| 1936 | D | 788 | 209 | 1,002 | |
| 1932 | D | 783 | 166 | 953 | |
| 1928 | R | 229 | 571 | 800 | |
| 1924 | D | 326 | 95 | 453 | |
| 1920 | D | 264 | 101 | 395 | |
| 1916 | D | 229 | 43 | 291 | |
| 1912 | D | 242 | 44 | 413 | |
| 1908 | — | — | — | — | |
| 1904 | — | — | — | — | |
| 1900 | — | — | — | — | |
| 1896 | — | — | — | — | |
| 1892 | — | — | — | — | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Zavala County, anchored by Crystal City, runs heavily Democratic in statewide contests, though its D+14.4 margin in 2024 reflects a notable rightward shift from the double-digit Democratic leads that once exceeded 40 points in this predominantly Hispanic, rural border region.
The Democratic margin in Zavala County peaked at sixty-nine points in 2008. By 1976 the county had flipped, voting Republican for the first time in many years. The 2024 margin was fourteen points, the most Democratic-leaning result in the county's modern history.
The economic context is the key. Zavala County's median household income of $36,749 sits well below state and national norms, and 34% of residents live below the federal poverty line. The shift here is part of a broader realignment of working-class places across the country. The county's voting pattern over the last decade is most similar to that of Dimmit County and Charles City County.