Mercer County, Ohio combines general rural western Ohio conservatism with a relative low level of unemployment that negates most economic populism. The county has a large number of family farms and surprising number of decent paying manufacturing jobs mostly at smaller nonunion companies. A lot of union presence disappeared when the Huffy Bike plant shut down in the 90's. It still has one of the lowest unemployment rates in the state, though it's more than doubled in the last 2 years.
What really sets the county off politically is the high number of Catholics, mostly of German heritage. Most of the surrounding counties share that demographic (and the resulting conservatism), but Mercer County has a particularly large share, especially in the southern half of the county.
These folks aren't any more or less wingnut in their conservatism than much of rural Ohio on most issues. The strong exception to this rule is abortion. That's not to say the region is full of extremists ready to bomb clinics, but its overwhelming how utterly ubiquitous hardcore opposition to abortion is even compared to typical midwestern small towns, and an absolute deal-breaker for any remotely pro-choice candidate.
It's ironic to consider that as recent as 1972 Mercer County was actually voting more Democratic than the statewise average. Check out the 1968 map. http://uselectionatlas.org/RESULTS/
The lonely red county on the Indiana border is Mercer. The rise of the abortion issue changed everything, though, and combined with (relative) economic prosperity on top of generic rural west Ohio conservatism together changed this once Democratic leaning county to the most GOP in the state in 2006 and 2008 (and probably 2010 as well).