| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | D | 1,155 | 850 | 2,080 | |
| 2020 | D | 1,311 | 741 | 2,094 | |
| 2016 | D | 1,125 | 588 | 1,848 | |
| 2012 | D | 1,340 | 446 | 1,837 | |
| 2008 | D | 1,245 | 415 | 1,697 | |
| 2004 | D | 1,170 | 566 | 1,760 | |
| 2000 | D | 1,054 | 504 | 1,648 | |
| 1996 | D | 1,168 | 333 | 1,641 | |
| 1992 | D | 1,180 | 366 | 1,753 | |
| 1988 | D | 1,120 | 454 | 1,581 | |
| 1984 | D | 997 | 621 | 1,631 | |
| 1980 | D | 1,036 | 489 | 1,583 | |
| 1976 | D | 1,033 | 392 | 1,454 | |
| 1972 | D | 744 | 602 | 1,428 | |
| 1968 | D | 933 | 477 | 1,482 | |
| 1964 | D | 1,284 | 299 | 1,589 | |
| 1960 | D | 1,351 | 637 | 2,001 | |
| 1956 | D | 1,256 | 958 | 2,254 | |
| 1952 | D | 1,369 | 1,070 | 2,447 | |
| 1948 | D | 1,563 | 921 | 2,532 | |
| 1944 | D | 1,515 | 896 | 2,416 | |
| 1940 | D | 1,698 | 1,121 | 2,845 | |
| 1936 | D | 1,518 | 930 | 2,504 | |
| 1932 | D | 1,475 | 707 | 2,215 | |
| 1928 | D | 1,070 | 657 | 1,760 | |
| 1924 | R | 665 | 755 | 1,561 | |
| 1920 | R | 750 | 778 | 1,571 | |
| 1916 | D | 1,028 | 579 | 1,671 | |
| 1912 | R | 567 | 1,072 | 1,947 | |
| 1908 | R | 559 | 1,051 | 1,627 | |
| 1904 | R | 506 | 917 | 1,445 | |
| 1900 | R | 453 | 884 | 1,351 | |
| 1896 | D | 1,052 | 374 | 1,434 | |
| 1892 | R | 0 | 526 | 829 | |
| 1888 | R | 383 | 507 | 898 | |
| 1884 | R | 484 | 498 | 982 | |
| 1880 | D | 379 | 334 | 713 | |
| 1876 | — | — | — | — |
Despite sparse population and an agricultural economy centered on the upper Rio Grande, Costilla County has returned double-digit Democratic margins in recent cycles, driven largely by a majority-Hispanic electorate with deep multigenerational roots in the region.
The Democratic margin in Costilla County reached its widest at sixty-two points in 1964. The margin in 2024 was fifteen points — still decisive.
Costilla County's loyalty is rooted in its place. Median household income of $36,861, a 44% non-Hispanic-white share, and a population of 3,607 together describe a community whose political habits are deeply settled. The county's voting pattern over the last decade is most similar to that of Charles City County and Rio Arriba County.
