| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 19,247 | 60,752 | 80,930 | |
| 2020 | R | 16,464 | 54,628 | 72,020 | |
| 2016 | R | 10,988 | 44,382 | 57,606 | |
| 2012 | R | 10,496 | 37,661 | 48,838 | |
| 2008 | R | 12,912 | 36,685 | 50,050 | |
| 2004 | R | 12,325 | 34,818 | 47,422 | |
| 2000 | R | 11,778 | 26,202 | 38,726 | |
| 1996 | R | 12,817 | 16,246 | 32,473 | |
| 1992 | R | 12,030 | 13,473 | 37,202 | |
| 1988 | R | 12,507 | 17,509 | 30,171 | |
| 1984 | R | 9,148 | 18,254 | 27,474 | |
| 1980 | R | 10,542 | 11,411 | 22,454 | |
| 1976 | D | 10,864 | 7,194 | 18,127 | |
| 1972 | R | 3,968 | 10,042 | 14,136 | |
| 1968 | D | 5,330 | 4,372 | 12,411 | |
| 1964 | D | 6,381 | 3,251 | 9,642 | |
| 1960 | R | 3,844 | 4,510 | 8,431 | |
| 1956 | R | 3,560 | 3,750 | 7,340 | |
| 1952 | D | 4,496 | 3,985 | 8,485 | |
| 1948 | D | 4,042 | 707 | 5,202 | |
| 1944 | D | 4,757 | 546 | 5,896 | |
| 1940 | D | 5,532 | 649 | 6,183 | |
| 1936 | D | 4,281 | 337 | 4,647 | |
| 1932 | D | 4,858 | 530 | 5,405 | |
| 1928 | R | 1,981 | 3,181 | 5,166 | |
| 1924 | D | 4,600 | 851 | 5,761 | |
| 1920 | D | 3,041 | 661 | 4,224 | |
| 1916 | D | 3,040 | 275 | 3,497 | |
| 1912 | D | 2,473 | 109 | 3,063 | |
| 1908 | — | — | — | — | |
| 1904 | — | — | — | — | |
| 1900 | — | — | — | — | |
| 1896 | — | — | — | — | |
| 1892 | — | — | — | — | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Anchoring the southwestern corner of the Dallas–Fort Worth metroplex, Johnson County has grown steadily as suburban sprawl pushes outward, yet its presidential margins have remained among the widest in the region.
The unraveling was not abrupt. The Democratic margin in Johnson County peaked at eighty-five 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 four points. By 2024, the margin had widened further.
The economic and demographic context is severe. Johnson County's median household income of $84,859 is among the lowest of any county in the United States; 10% of residents live below the federal poverty line. The county's voting pattern over the last decade is most similar to that of Wichita County and Brown County.