| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 3,070 | 5,379 | 8,616 | |
| 2020 | R | 3,577 | 5,303 | 9,048 | |
| 2016 | R | 3,196 | 4,971 | 8,866 | |
| 2012 | D | 4,768 | 4,098 | 9,017 | |
| 2008 | D | 4,899 | 3,820 | 8,850 | |
| 2004 | D | 4,487 | 4,456 | 9,001 | |
| 2000 | D | 4,045 | 4,034 | 8,315 | |
| 1996 | D | 3,994 | 2,986 | 7,752 | |
| 1992 | D | 3,573 | 2,948 | 8,330 | |
| 1988 | D | 4,584 | 3,362 | 8,012 | |
| 1984 | R | 4,061 | 4,882 | 8,990 | |
| 1980 | R | 3,049 | 4,840 | 8,602 | |
| 1976 | D | 4,580 | 4,379 | 9,107 | |
| 1972 | R | 3,693 | 5,058 | 8,880 | |
| 1968 | R | 3,767 | 4,955 | 9,253 | |
| 1964 | D | 6,057 | 3,543 | 9,608 | |
| 1960 | R | 4,950 | 5,535 | 10,486 | |
| 1956 | R | 4,795 | 5,952 | 10,773 | |
| 1952 | R | 4,076 | 7,061 | 11,154 | |
| 1948 | D | 5,115 | 4,763 | 10,028 | |
| 1944 | D | 5,286 | 5,249 | 10,567 | |
| 1940 | D | 5,996 | 5,865 | 11,893 | |
| 1936 | D | 6,625 | 4,737 | 11,522 | |
| 1932 | D | 6,704 | 4,051 | 10,920 | |
| 1928 | R | 4,798 | 5,589 | 10,432 | |
| 1924 | R | 2,180 | 5,177 | 9,367 | |
| 1920 | R | 2,552 | 6,352 | 9,073 | |
| 1916 | R | 2,572 | 3,061 | 5,735 | |
| 1912 | D | 2,446 | 1,179 | 5,465 | |
| 1908 | R | 2,550 | 2,774 | 5,572 | |
| 1904 | R | 2,360 | 3,127 | 5,673 | |
| 1900 | R | 2,736 | 3,290 | 6,155 | |
| 1896 | R | 2,596 | 3,054 | 5,733 | |
| 1892 | D | 2,589 | 2,421 | 5,138 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Tama County is home to the Meskwaki Settlement, one of the few tribally owned land parcels in the Midwest purchased outright rather than held in federal trust, giving the county an unusual demographic and jurisdictional layer beneath its otherwise rural, agricultural profile.
The county's recent history is a story of close margins. The Democratic margin reached twenty-six points in 1964; the Republican margin reached forty-two points in 1920. Most other elections have been decided by single-digit points.
Tama County's demographics — a population of 16,868, a 80% non-Hispanic-white share, a median household income of $70,781 — situate the county close to national averages on several dimensions. The county's voting pattern over the last decade is most similar to that of Cedar County and Webster County.