Lets talk facts for a minute, since they seem to be listed by John, but conveniently overlooked...
Detroit is a predominantly Black city, as is the surrounding 'burbs - which we'll just call "non-white" to simplify any arguments.
Very few white GOP's actually live in Detroit.
In 2008, 97% of ALL black voters nationwide voted for Obama. No matter where they lived.
Out of the voters who would vote GOP in Detroit (which are few), I could see the majority of them voting Paul. I have no argument with that.
Now... when the actual Presidential stuff happens, in November, Detroit is gonna vote for Obama in a landslide.
Michigan, overall, I think will get Romney as their GOP, and then be overwhelmed by Obama supporters.
It probably won't even be close.