The 1998 United States Senate election in Idaho was held November 3, 1998 alongside other elections to the United States Senate in other states as well as elections to the United States House of Representatives and various state and local elections. Incumbent Republican U.S. Senator Dirk Kempthorne decided to retire after one term to run for governor. Republican nominee Mike Crapo won the open seat.
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County results
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| Party | Candidate | Votes | % | |
|---|---|---|---|---|
| Democratic | Bill Mauk | 22,503 | 100.00% | |
| Total votes | 22,503 | 100.00% | ||
| Party | Candidate | Votes | % | |
|---|---|---|---|---|
| Republican | Mike Crapo | 110,205 | 87.27% | |
| Republican | Matt Lambert | 16,075 | 12.73% | |
| Total votes | 126,280 | 100.00% | ||
| Party | Candidate | Votes | % | ±% | |
|---|---|---|---|---|---|
| Republican | Mike Crapo | 262,966 | 69.54% | +13.01% | |
| Democratic | Bill Mauk | 107,375 | 28.39% | −15.08% | |
| Natural Law | George J. Mansfeld | 7,833 | 2.07% | +2.07% | |
| Majority | 155,591 | 41.14% | +28.10% | ||
| Turnout | 378,174 | −20.97% | |||
| Republican hold | |||||
