A head to head comparison of the 2008 Idaho General Election gives us an idea of the break down of the voters.    

John McCain received 403,012 (62%) votes, beating Barack Obama who gained 236,440 (36%) by 166,572 votes in Idaho.

John McCain won 41 counties whereas Barack Obama won 3 counties in the total of the 44 counties in the State of Idaho.

Presidential General Elections

During the 2008 General elections, over 131M total number of votes were cast. Barack Obama got 69,448,278 (69.4 Million) over John McCain's 61,739,059 (61.7 Million). He won the popular vote by 7,709,219 (7.7 Million). Even though he lost to John McCain in the State of Idaho, his 236,440 votes represents 0.3% of his popular vote victory. The remaining 49 states contributed to the remaining 99.7% popular votes victory.

Top 15 Counties in Primary Elections vs General Elections

All Candidates (General Elections)

These 15 counties play an important role in these Primary elections. If a candidate, can get a sizable majority in the largest counties (Ada, Canyon, Kootenai, Bonneville), it becomes very difficult to win majorities in the smaller counties without voter outreach and increased voter participation in them.

Top 15 Counties Comparison in Primary Elections vs General Elections

General Elections
Barack Obama

General Elections
John McCain

Ada, Canyon, Kootenai and Bonneville), four of the largest counties, voted in favor of John McCain giving him a 67k vote advantage. This, combined with John McCain's steady marginal wins in the less popular counties were enough maintain that lead over Barack Obama, making him gain an upper hand in the State of Idaho.

Related References: 2016 Idaho Primary Election Story, 2016 Idaho General Election Story, 2020 Idaho Primary Election Story, 2020 Idaho General Election Story, 2012 Idaho General Election Story