For some reason, I picked up the lesser known south MI country accent commonly heard outside of Adrian, Jackson, and Hillsdale. I didn't realize it until I did some work there and realized they talked like me. Grandpa's from Jackson, and dad worked the auto factories, so I picked a little of that up.
Interesting question!
I went to college with several Cranbook and Detroit County Day School people so I understand the attempt of some of their graduates to sound refined and cultured in their clipped quasi-Yankee speech. Maybe that will help the graduates if they get into Harvard or Yale but I can't imagine it helping Romney in the South.
I grew up in Grand Rapids and lived most of my life until the last dozen years in either Holland, Grand Rapids, or the rural area west of Kalamazoo, which means basically the “Hollandse colonie” of the Dutch. Other than learning how to mangle some Dutch pronunciations -- try saying Christelijke Gereformeerden five times fast with proper guttural vocalizations -- I don't think that ethnic proximity had any effect on my speech.
However, my parents both came from families that had spent several generations in northern Michigan since shortly after the Civil War. My mother was from Traverse City and my father was a Yooper (Michigan's Upper Peninsula for the Southerners reading this thread who have no idea what we're talking about.) My father's family moved to Flint during WW2 to work in the war defense plants and later my father traveled all over the Southern US during his time in the military; my mother's family moved to the Battle Creek-Kalamazoo area but she spent most summers with family in Traverse City.
Where this becomes relevant is that because my parents grew up before the age of television, they spoke with a pronounced accent that isn't heard today in Michigan, and the only thing I've heard much like it is the rural farm accent of people from Bob Dole's generation in the upper Midwest. I grew up with the nasal twang of a West Michigander which was once shared all along the Lakeshore; the standard joke was that due to bad weather we always had our noses stuffed up and couldn't talk right.
I don't know that this has anything to do with the subject at hand, but you asked, so I hope at least one person was interested!