Democrat Curt Hanson won by a margin of just 107 votes in a special election earlier this month in Iowa’s House District 90. The race was interesting because off-year elections allow you to take the temperature of politics.

This race was also interesting because it was the first contest after the Iowa Supreme Court ruled that gay marriage in Iowa is a constitutionally protected civil liberty. Because it was the first test of how the gay-marriage issue might play out, outside groups poured huge amounts of money into the race. The National Organization for Marriage was especially prominent, and pro-gay marriage groups also opened their wallets more than you’d expect in such a basically insignificant contest.

So what does the victory of Hanson tell us?

First, it tells us that the gay-marriage issue, which was the prominent campaign theme, was not enough to swing this election.

Second, it tells us very little about support for gay marriage because although Republican Stephen Burgmeier was the recipient of the anti-gay marriage largesse, Hanson is also not a gay-marriage supporter. Let it be said that outsiders actually stoked the emphasis on gay marriage. Burgmeier himself may not have made that the central storm of the race.

Third, the loss was a big disappointment for the GOP, judging by the private reactions of Republicans I’ve spoken with.

Fourth, this race puts the question of whether gay marriage is a good issue for Republicans to run on in 2010 front and center.

Fifth, the pending announcement that former Iowa Gov. Terry Branstad will run for governor has underscored the necessity of the GOP to use its former winning strategy of walking down the political center. Both Branstad and former Gov. Robert Ray were very successful at concentrating on non-divisive issues and harvesting majorities of voters in the state.

Sixth, the race suggests that the GOP needs to re-examine its bigger course. The party is running behind both “no-party” and Democrats in registered voters. The Iowa GOP appears to have moved into the quadrant of “ideological political party,” where it adheres to clear and hard positions on social issues, regardless of Iowa voters’ concerns.

Republicans were trounced in the 2008 elections in part because of the true believers on the conservative right, especially media celebrities such as Rush Limbaugh, Michael Savage, and Glenn Beck. They attacked Republican candidate Sen. John McCain, R-Ariz., for not being conservative enough, which pushed McCain to the right on issues and lost him the vital independents that both parties need to peel off to win elections.

The recent Iowa House race is a very interesting case study of how all these issues come together, and it forces the GOP and its candidates to study the results. On the other hand, for supporters of gay marriage and for Democrats in Iowa, the race is a cautionary tale: The Democrat who won is not a gay-marriage supporter.

Steffen Schmidt is a political-science professor at Iowa State University.