White ethnic groups more likely to vote Republican than whites in general

Looking at GSS data, I noticed that there were a few white ethnic groups who were more likely than whites in general to vote for Bush in 2004 (the most recent year available): English/Welsh, Scottish, Scots-Irish, Dutch, German, and Swedish. Why?

I checked to see if perhaps income or small-town residency might explain the tendency. Here are the logistic regression coefficients (sample size = 1,773):

Logistics regression coefficients

English .53*
Scottish .22
Scots Irish .30
Dutch 1.23*
German .62*
Swedish .43
Income .10*
Town size -.01

*statistically significantly

Even after adjusting for income and population, Americans of English, Dutch, and German descent are more likely than other whites to vote Republican. (All groups have positive coefficients). I wonder if these people tend to be attracted to conservatism because it is more backward-looking, and many from the groups have American ancestors that go way back. They might feel a stronger connection because of having deep American roots to the Founding Fathers who are associated with limited government and conservative values.  Their voting tendencies might be subconsciously influenced by their ethnicity. One the other hand, perhaps its just the default position for Americans who have been completely stripped of ethnicity.