The last few votes are still being counted, and as of this writing Sen. Rick Santorum is on the verge of a stunning upset victory over Gov. Mitt Romney in the Iowa caucuses, leading by a margin of just several dozen votes.

(Update: The lead has changed hands yet again, with a few results still out. Update: And again! Now Santorum’s 5 votes up. Update 1:34 a.m. CST: Romney has now won by only 8 votes. What a ride.)

Yet regardless of who finds more votes in the final boxes, it seems clear that Iowa’s conservatives have chosen Santorum.

The maps below say it all.

The upper map is from the Des Moines Register, and shows the county-by-county results in tonight’s caucuses. The red counties are those where Santorum has won or is leading; the blue counties are going for Romney, and the yellow counties to Paul. (Two counties in pink went to Perry; Gingrich, who bested Perry statewide, did not win any counties.)

The lower map is from the New York Times, and shows the county-by-county election results from November 2008.

It’s clear that while Romney and Paul have largely won in areas that went for Barack Obama, Santorum’s wins have tended to come in areas that voted for John McCain.

That result suggests that while Romney is still in the best position to win the Republican nomination, he has not yet sealed the deal with the conservative base. With several of the campaigns likely to shut down in the next few weeks–or days–Santorum could quickly cement his support as the conservative alternative to Romney.

The close match between Romney/Paul counties and Obama 2008 counties also complicates Romney’s argument that he is the most electable Republican. He may do better among moderate Republicans, independents, and crossover Democrats, but if he cannot motivate the party’s core supporters, he may not be able to prevail against Obama.

The Republican Party may be closer to finding its nominee after tonight–but it may have a long way to go before it finds its winning formula.