| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 24,880 | 51,588 | 78,059 | |
| 2020 | R | 24,376 | 51,219 | 77,258 | |
| 2016 | R | 17,318 | 45,456 | 67,147 | |
| 2012 | R | 17,260 | 39,513 | 58,092 | |
| 2008 | R | 21,553 | 36,487 | 58,644 | |
| 2004 | R | 13,109 | 37,765 | 51,255 | |
| 2000 | R | 11,952 | 29,404 | 42,284 | |
| 1996 | R | 11,278 | 23,733 | 39,259 | |
| 1992 | R | 8,712 | 20,353 | 37,438 | |
| 1988 | R | 9,001 | 24,654 | 33,778 | |
| 1984 | R | 7,715 | 23,482 | 31,368 | |
| 1980 | R | 8,445 | 20,018 | 30,174 | |
| 1976 | R | 10,075 | 16,414 | 26,749 | |
| 1972 | R | 5,067 | 17,537 | 22,724 | |
| 1968 | R | 5,946 | 12,089 | 21,111 | |
| 1964 | R | 10,099 | 10,472 | 20,663 | |
| 1960 | R | 7,400 | 12,426 | 19,919 | |
| 1956 | R | 6,125 | 10,125 | 16,291 | |
| 1952 | R | 5,909 | 9,119 | 15,082 | |
| 1948 | D | 6,216 | 6,151 | 12,454 | |
| 1944 | R | 5,426 | 6,194 | 11,673 | |
| 1940 | R | 6,350 | 6,451 | 12,857 | |
| 1936 | D | 6,934 | 5,315 | 12,329 | |
| 1932 | D | 6,940 | 4,593 | 11,718 | |
| 1928 | R | 4,548 | 5,513 | 10,152 | |
| 1924 | R | 4,699 | 4,954 | 9,757 | |
| 1920 | D | 5,452 | 4,863 | 10,722 | |
| 1916 | D | 3,108 | 2,428 | 5,737 | |
| 1912 | D | 2,890 | 924 | 5,495 | |
| 1908 | D | 3,268 | 2,519 | 5,992 | |
| 1904 | D | 2,882 | 2,574 | 5,792 | |
| 1900 | D | 3,088 | 2,367 | 5,643 | |
| 1896 | D | 3,083 | 2,288 | 5,458 | |
| 1892 | D | 2,606 | 2,093 | 5,099 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Johnson County has added tens of thousands of residents over two decades of suburban sprawl south of Indianapolis, yet its presidential margins have remained among the widest in the state, hitting R+34.3 in 2024.
The Republican margin in Johnson County reached its widest at fifty-five points in 1972. The margin in 2024 was thirty-four points, in line with the county's deep historical pattern.
Johnson County's loyalty is rooted in its place. Median household income of $90,454, a 85% non-Hispanic-white share, and a population of 166,315 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 Hancock County and Rockingham County.
