| County | Constitution | Democratic | Libertarian | Republican | Unaffiliated | Total Registered |
|---|---|---|---|---|---|---|
| Ada | 575 | 41,817 | 2,556 | 101,240 | 90,375 | 236,563 |
| Adams | 15 | 171 | 15 | 1,673 | 652 | 2,526 |
| Bannock | 130 | 4,450 | 376 | 17,197 | 18,163 | 40,316 |
| Bear Lake | 16 | 108 | 7 | 2,581 | 584 | 3,296 |
| Benewah | 26 | 520 | 25 | 2,430 | 2,047 | 5,048 |
| Bingham | 76 | 1,481 | 75 | 12,411 | 5,200 | 19,243 |
| Blaine | 10 | 2,698 | 106 | 3,301 | 6,588 | 12,703 |
| Boise | 24 | 329 | 35 | 2,828 | 1,356 | 4,572 |
| Bonner | 149 | 2,398 | 209 | 14,552 | 7,631 | 24,939 |
| Bonneville | 151 | 3,597 | 358 | 29,366 | 17,027 | 50,499 |
| Boundary | 24 | 423 | 49 | 4,094 | 1,528 | 6,118 |
| Butte | 5 | 59 | 5 | 1,146 | 262 | 1,477 |
| Camas | 5 | 30 | 5 | 455 | 186 | 681 |
| Canyon | 399 | 8,820 | 758 | 45,100 | 31,319 | 86,396 |
| Caribou | 19 | 99 | 10 | 2,683 | 819 | 3,630 |
| Cassia | 28 | 443 | 32 | 6,698 | 2,027 | 9,228 |
| Clark | 2 | 17 | 2 | 314 | 51 | 386 |
| Clearwater | 9 | 367 | 24 | 2,238 | 1,699 | 4,337 |
| Custer | 4 | 137 | 16 | 2,015 | 614 | 2,786 |
| Elmore | 35 | 920 | 73 | 5,831 | 3,172 | 10,031 |
| Franklin | 38 | 164 | 28 | 4,593 | 1,254 | 6,077 |
| Fremont | 29 | 266 | 19 | 5,037 | 1,287 | 6,638 |
| Gem | 43 | 590 | 52 | 6,073 | 2,588 | 9,346 |
| Gooding | 22 | 522 | 34 | 3,739 | 1,783 | 6,100 |
| Idaho | 36 | 538 | 53 | 6,583 | 2,357 | 9,567 |
| Jefferson | 41 | 397 | 48 | 9,946 | 2,852 | 13,284 |
| Jerome | 122 | 649 | 37 | 4,386 | 2,690 | 7,884 |
| Kootenai | 314 | 8,273 | 624 | 42,550 | 26,295 | 78,056 |
| Latah | 85 | 4,217 | 300 | 7,569 | 9,680 | 21,851 |
| Lemhi | 9 | 357 | 22 | 3,197 | 1,170 | 4,755 |
| Lewis | 7 | 152 | 7 | 1,240 | 607 | 2,013 |
| Lincoln | 7 | 162 | 14 | 1,339 | 605 | 2,127 |
| Madison | 84 | 519 | 162 | 12,941 | 4,400 | 18,106 |
| Minidoka | 21 | 516 | 27 | 4,887 | 2,194 | 7,645 |
| Nez Perce | 69 | 2,412 | 118 | 8,536 | 9,803 | 20,938 |
| Oneida | 7 | 91 | 15 | 1,876 | 460 | 2,449 |
| Owyhee | 26 | 344 | 27 | 3,127 | 1,313 | 4,837 |
| Payette | 37 | 862 | 56 | 6,241 | 3,507 | 10,703 |
| Power | 6 | 376 | 12 | 1,696 | 1,162 | 3,252 |
| Shoshone | 21 | 1,350 | 23 | 2,403 | 2,555 | 6,352 |
| Teton | 16 | 1,162 | 50 | 2,407 | 2,377 | 6,012 |
| Twin Falls | 134 | 2,827 | 239 | 19,524 | 11,640 | 34,364 |
| Valley | 16 | 866 | 31 | 3,290 | 2,070 | 6,273 |
| Washington | 7 | 376 | 20 | 3,523 | 1,189 | 5,115 |
| Total | 2,899 | 96,872 | 6,754 | 424,856 | 287,138 | 818,519 |