Idaho is a winner-take-all caucus with 32 delegates. However, the proces to get to winner-take-all is a bit complicated. From the Idaho GOP party rules:
Section 7: Voting takes place in successive rounds. After each round, the candidate receiving the fewest votes and any candidate(s) receiving fewer than 15% of the Caucus vote are removed from the ballot. Voting continues until a single candidate receives greater than 50% of the vote, or until a final vote is taken for the final two candidates.
Section 10: At the end of each round of voting, the County Chairman shall announce the results. Voting continues until a single candidate receives greater than 50% of the vote or until a final vote is taken for two remaining candidates. After the final round of voting, the County Chairman shall phone the final results to the Idaho Republican Party Chairman.
Section 4: Any candidate winning greater than 50% of a county’s vote will be awarded that entire county’s share of National Delegates. When neither candidate wins greater than 50%, the candidates will split the county’s share of National Delegates, in proportion to the candidates’ county vote totals.
Section 5: The sum of all the Counties’ shares for each candidate, rounding the sum to the nearest whole delegate, will be that candidate’s share of the Delegates and Alternates to the National Convention with the proviso that, if one candidate wins more than 50% of the Idaho allotment of delegates, that candidate shall receive the entire 100% of the allotment of Delegates and Alternates to the National Convention. If the computation results in an unallocated Delegate, the Delegate shall be assigned to the candidate receiving the highest number of votes in the Idaho Caucus. If the computation results in the allocation of more Delegates than are available for allocation, the Delegate assignment to the candidate receiving the least number of Caucus votes shall be reduced accordingly.As we shall see, Romney is the candidate most likely to reach this winner-take-all scenario. However, if we see a situation where Paul, Romney and Santorum each win a solid number of counties, then the state essentially turns into a draw in the delegate race.
Idaho did not require party registration until July 1st of last year, so a substantial number of voters remain unaffiliated. The primary is closed, but voters may still declare for a party at the polls (which always helps Paul).
By the time Idaho voted in 2008, John McCain had essentially clinched the nomination. Only Paul remained in the contest, carrying his lonely crusade all the way to a counter-convention in Minneapolis. Further, the lack of a prominent Mormon candidate at that stage in the contest further undermines the value of the 2008 results. Finally, the 2008 contest was a primary rather than a caucus. John McCain took 70%; Ron Paul 24%.
Mitt Romney's big edge here is the Mormon vote. Romney won 88% of Mormons in Nevada and 96% in Arizona, according to CNN exit polling. Micah Cohen (at FiveThirtyEight) cites Idaho GOP Executive Director Jonathan Parker as estimating that 1/3rd of caucus-goers will be Mormon. Plugging in a floor of 80% support, a conservative estimate, among Mormons for Romney locks up 26% of the Republican electorate walking in, a sizable barrier for any other candidate to surmount. Many of these voters are in the east and southeastern portions of the state, so watch for large margins for Romney here.
More unpredictable than the actual degree of Mormon support for Romney is turnout. On the one hand, the contest is still ongoing, driving the desire of voters to make their voice heard. On the other hand, caucuses with set times and longer durations tend to be less attended than primary contests. Anecdotally, the Spokesman Review claims that this may be similar to Washington, which experienced higher-than-anticipated turnout after the switch to a primary.
The Paul and Romney campaigns have focused significant attention on Idaho, as has Santorum to a somewhat lesser extent. Romney has run small ads in the state, but the competition essentially amounts to turnout. Paul's coalition, which relies upon youth voters and independents turning out, will be going up against the Mormon vote and Romney's strong establishment support (many elected office-holders, including Governor Butch Otter and Rep. Mike Simpson, have endorsed Romney). Both candidates drew crowds of over 1,000 in recent visits to the state. While Paul will likely over-perform on college campuses (excluding Brigham Young's affiliate here), he has had trouble turning out enough of this coalition to outweigh the traditional Republican electorate in past contests. When considering Romney's high floor here, Paul will likely have trouble.
Cohen argues that Santorum will rely upon evangelical Catholics in the southwestern part of the state and Catholics and Protestants in the northwest. If Santorum can run up his margins among these voters, he can create a broad-based coalition that could challenge Romney's strength with Mormons. However, it looks like Romney is taking no chances on an organizational level here, and I am skeptical Santorum can run up high enough margins among this constituency to contest the state. I still give Romney the strong advantage.
Gingrich, who recently switched largely to a Southern strategy in the run-up to Super Tuesday, appears to be left with no natural base of support.
Without any real polls, the contest boils down to turnout. Each campaign has a constituency to target- Romney's is just the most reliable.