how does Michele Bachmann keep winning renomination?

[I spent the winter writing songs about getting better]

It seems like she's done just about everything you're not supposed to do as a jr member of congress and someone the MNGOP would want to primary. It surprises me, given the overall makeup of the district, that she even won the primary initially. Isn't her district, SES-wise similar to the Ramstad district?

No, not at all. MN-03 is mostly affluent, upper-middle class suburbs, at least those are the areas that vote Republican. MN-06 is mostly working class exurbs.

Also our convention system benefits more conservative candidates in the GOP primary (and more liberal ones in the DFL one.) That's her biggest benefit.

[I spent the winter writing songs about getting better]

That's not an exurb. It's closer to downtown Dallas than downtown Fort Worth is.

[I spent the winter writing songs about getting better]

These are the type of places in her district that vote for her:

http://www.city-data.com/city/Oak-Grove-Minnesota.html
http://www.city-data.com/city/Elk-River-Minnesota.html
http://www.city-data.com/city/Buffalo-Minnesota.html

Now I know they might look relatively high income, but consider that they have a much higher rate of married couples who are filing jointly. Note the education rates. It's not too surprising that someone with a college degree is much less likely to vote for someone like Michele Bachmann.

[I spent the winter writing songs about getting better]

FWIW, the policy described in the article has now been repealed, and was almost unanimously. And Anoka County normally wouldn't elect people like Bachmann, but the district lacks the appendage that runs down to Minneapolis (which is quite Democratic) and the town of Coon Rapids (a swing area that wouldn't vote for her.) Bachmann's support mostly comes further out places like Tom Emmer's home county of Wright, and Sherburne which famously used to elect a State Rep who compared Democrats blocking the gay marriage amendment to communist persecution of Christians, and was primaried after being arrested and convicted for beating his wife with the Bible (like literally. He'd strike and toss Bibles at her.) Sherburne County is also home to a car dealership know for its sign which frequently changes to random Bible verses, and Wright County is formerly home to this bank which was later shut down by state regulators in 2009.

[I spent the winter writing songs about getting better]

...there are fundamentalists that aren't Baptists. Nor are all Baptists fundamentalists or like Southern Baptists, (St. Paul's trendsetting, influential and decidedly progressive House of Mercy church started as an American Baptist affiliate.)

Our conservative evangelicals are mostly conservative Lutherans (LCMS and WELS), Assembly of God, and some non-denominational megachurch type places (most of which are basically Baptist in theology but don't affiliate with any Baptist group and won't show up on the map). Remember that according to the exit poll in 2008, 29% of voters in Minnesota identified as white evangelicals, and though Obama won a surprisingly large 35% of them, that was no doubt quite a bit lower in Bachmann's district (liberal evangelicals in the actual Twin Cities are not uncommon at all.)