BOOM: New poll shows Romney leading Obama by 1 in Michigan

Full results here. The sample is 44% Democrat, 35% Republican, and 21% Independent, or D+9 (see page 22).

By comparison, turnout in the 2008 presidential election, when Obama-mania was at its peak, was D+12.

So D+9 seems like a reasonable (that is, unskewed) sample.