From Quinnipiac/washingtonpost.com/Wall Street Journal poll:

Colorado: McCain 46, Obama 44

Michigan: Obama 46, McCain 42

Minnesota: Obama 46, McCain 44

Wisconsin: Obama 50, McCain 39

Read more — including whats battleground voters think of the potential First Ladies — here.

Dates conducted: July 14-22. Error margins: Range from 2.4 to 3 points.