Predictions for tonight's primaries;
Romney will win the popular vote in Michigan by a slim margin; 2, maybe three percentage points. However, Santorum will win more congressional districts, and thus more delegates, because of how Michigan handles delegate selection.
Romney will win Arizona. It will be much closer than expected, but Arizona is winner take all, so there won't be any narrative there other than 'Romney won Arizona', even if it's insanely close.